CVE-2016-0799
📋 TL;DR
CVE-2016-0799 is a buffer overflow vulnerability in OpenSSL's fmtstr function that allows remote attackers to cause denial of service or potentially execute arbitrary code by sending specially crafted long strings. It affects OpenSSL versions 1.0.1 before 1.0.1s and 1.0.2 before 1.0.2g. Any system or application using vulnerable OpenSSL versions for cryptographic operations is at risk.
💻 Affected Systems
- OpenSSL
- Applications using OpenSSL libraries
- Systems with OpenSSL packages
📦 What is this software?
Client by Pulsesecure
Client by Pulsesecure
Openssl by Openssl
OpenSSL is a robust, commercial-grade toolkit for the Transport Layer Security (TLS) and Secure Sockets Layer (SSL) protocols. It provides cryptographic functions and is one of the most widely used libraries for implementing secure communications in applications worldwide.
Learn more about Openssl →Openssl by Openssl
OpenSSL is a robust, commercial-grade toolkit for the Transport Layer Security (TLS) and Secure Sockets Layer (SSL) protocols. It provides cryptographic functions and is one of the most widely used libraries for implementing secure communications in applications worldwide.
Learn more about Openssl →Openssl by Openssl
OpenSSL is a robust, commercial-grade toolkit for the Transport Layer Security (TLS) and Secure Sockets Layer (SSL) protocols. It provides cryptographic functions and is one of the most widely used libraries for implementing secure communications in applications worldwide.
Learn more about Openssl →Openssl by Openssl
OpenSSL is a robust, commercial-grade toolkit for the Transport Layer Security (TLS) and Secure Sockets Layer (SSL) protocols. It provides cryptographic functions and is one of the most widely used libraries for implementing secure communications in applications worldwide.
Learn more about Openssl →Openssl by Openssl
OpenSSL is a robust, commercial-grade toolkit for the Transport Layer Security (TLS) and Secure Sockets Layer (SSL) protocols. It provides cryptographic functions and is one of the most widely used libraries for implementing secure communications in applications worldwide.
Learn more about Openssl →Openssl by Openssl
OpenSSL is a robust, commercial-grade toolkit for the Transport Layer Security (TLS) and Secure Sockets Layer (SSL) protocols. It provides cryptographic functions and is one of the most widely used libraries for implementing secure communications in applications worldwide.
Learn more about Openssl →Openssl by Openssl
OpenSSL is a robust, commercial-grade toolkit for the Transport Layer Security (TLS) and Secure Sockets Layer (SSL) protocols. It provides cryptographic functions and is one of the most widely used libraries for implementing secure communications in applications worldwide.
Learn more about Openssl →Openssl by Openssl
OpenSSL is a robust, commercial-grade toolkit for the Transport Layer Security (TLS) and Secure Sockets Layer (SSL) protocols. It provides cryptographic functions and is one of the most widely used libraries for implementing secure communications in applications worldwide.
Learn more about Openssl →Openssl by Openssl
OpenSSL is a robust, commercial-grade toolkit for the Transport Layer Security (TLS) and Secure Sockets Layer (SSL) protocols. It provides cryptographic functions and is one of the most widely used libraries for implementing secure communications in applications worldwide.
Learn more about Openssl →Openssl by Openssl
OpenSSL is a robust, commercial-grade toolkit for the Transport Layer Security (TLS) and Secure Sockets Layer (SSL) protocols. It provides cryptographic functions and is one of the most widely used libraries for implementing secure communications in applications worldwide.
Learn more about Openssl →Openssl by Openssl
OpenSSL is a robust, commercial-grade toolkit for the Transport Layer Security (TLS) and Secure Sockets Layer (SSL) protocols. It provides cryptographic functions and is one of the most widely used libraries for implementing secure communications in applications worldwide.
Learn more about Openssl →Openssl by Openssl
OpenSSL is a robust, commercial-grade toolkit for the Transport Layer Security (TLS) and Secure Sockets Layer (SSL) protocols. It provides cryptographic functions and is one of the most widely used libraries for implementing secure communications in applications worldwide.
Learn more about Openssl →Openssl by Openssl
OpenSSL is a robust, commercial-grade toolkit for the Transport Layer Security (TLS) and Secure Sockets Layer (SSL) protocols. It provides cryptographic functions and is one of the most widely used libraries for implementing secure communications in applications worldwide.
Learn more about Openssl →Openssl by Openssl
OpenSSL is a robust, commercial-grade toolkit for the Transport Layer Security (TLS) and Secure Sockets Layer (SSL) protocols. It provides cryptographic functions and is one of the most widely used libraries for implementing secure communications in applications worldwide.
Learn more about Openssl →Openssl by Openssl
OpenSSL is a robust, commercial-grade toolkit for the Transport Layer Security (TLS) and Secure Sockets Layer (SSL) protocols. It provides cryptographic functions and is one of the most widely used libraries for implementing secure communications in applications worldwide.
Learn more about Openssl →Openssl by Openssl
OpenSSL is a robust, commercial-grade toolkit for the Transport Layer Security (TLS) and Secure Sockets Layer (SSL) protocols. It provides cryptographic functions and is one of the most widely used libraries for implementing secure communications in applications worldwide.
Learn more about Openssl →Openssl by Openssl
OpenSSL is a robust, commercial-grade toolkit for the Transport Layer Security (TLS) and Secure Sockets Layer (SSL) protocols. It provides cryptographic functions and is one of the most widely used libraries for implementing secure communications in applications worldwide.
Learn more about Openssl →Openssl by Openssl
OpenSSL is a robust, commercial-grade toolkit for the Transport Layer Security (TLS) and Secure Sockets Layer (SSL) protocols. It provides cryptographic functions and is one of the most widely used libraries for implementing secure communications in applications worldwide.
Learn more about Openssl →Openssl by Openssl
OpenSSL is a robust, commercial-grade toolkit for the Transport Layer Security (TLS) and Secure Sockets Layer (SSL) protocols. It provides cryptographic functions and is one of the most widely used libraries for implementing secure communications in applications worldwide.
Learn more about Openssl →Openssl by Openssl
OpenSSL is a robust, commercial-grade toolkit for the Transport Layer Security (TLS) and Secure Sockets Layer (SSL) protocols. It provides cryptographic functions and is one of the most widely used libraries for implementing secure communications in applications worldwide.
Learn more about Openssl →Openssl by Openssl
OpenSSL is a robust, commercial-grade toolkit for the Transport Layer Security (TLS) and Secure Sockets Layer (SSL) protocols. It provides cryptographic functions and is one of the most widely used libraries for implementing secure communications in applications worldwide.
Learn more about Openssl →Openssl by Openssl
OpenSSL is a robust, commercial-grade toolkit for the Transport Layer Security (TLS) and Secure Sockets Layer (SSL) protocols. It provides cryptographic functions and is one of the most widely used libraries for implementing secure communications in applications worldwide.
Learn more about Openssl →Openssl by Openssl
OpenSSL is a robust, commercial-grade toolkit for the Transport Layer Security (TLS) and Secure Sockets Layer (SSL) protocols. It provides cryptographic functions and is one of the most widely used libraries for implementing secure communications in applications worldwide.
Learn more about Openssl →Openssl by Openssl
OpenSSL is a robust, commercial-grade toolkit for the Transport Layer Security (TLS) and Secure Sockets Layer (SSL) protocols. It provides cryptographic functions and is one of the most widely used libraries for implementing secure communications in applications worldwide.
Learn more about Openssl →Openssl by Openssl
OpenSSL is a robust, commercial-grade toolkit for the Transport Layer Security (TLS) and Secure Sockets Layer (SSL) protocols. It provides cryptographic functions and is one of the most widely used libraries for implementing secure communications in applications worldwide.
Learn more about Openssl →Openssl by Openssl
OpenSSL is a robust, commercial-grade toolkit for the Transport Layer Security (TLS) and Secure Sockets Layer (SSL) protocols. It provides cryptographic functions and is one of the most widely used libraries for implementing secure communications in applications worldwide.
Learn more about Openssl →Openssl by Openssl
OpenSSL is a robust, commercial-grade toolkit for the Transport Layer Security (TLS) and Secure Sockets Layer (SSL) protocols. It provides cryptographic functions and is one of the most widely used libraries for implementing secure communications in applications worldwide.
Learn more about Openssl →Openssl by Openssl
OpenSSL is a robust, commercial-grade toolkit for the Transport Layer Security (TLS) and Secure Sockets Layer (SSL) protocols. It provides cryptographic functions and is one of the most widely used libraries for implementing secure communications in applications worldwide.
Learn more about Openssl →Openssl by Openssl
OpenSSL is a robust, commercial-grade toolkit for the Transport Layer Security (TLS) and Secure Sockets Layer (SSL) protocols. It provides cryptographic functions and is one of the most widely used libraries for implementing secure communications in applications worldwide.
Learn more about Openssl →Openssl by Openssl
OpenSSL is a robust, commercial-grade toolkit for the Transport Layer Security (TLS) and Secure Sockets Layer (SSL) protocols. It provides cryptographic functions and is one of the most widely used libraries for implementing secure communications in applications worldwide.
Learn more about Openssl →Openssl by Openssl
OpenSSL is a robust, commercial-grade toolkit for the Transport Layer Security (TLS) and Secure Sockets Layer (SSL) protocols. It provides cryptographic functions and is one of the most widely used libraries for implementing secure communications in applications worldwide.
Learn more about Openssl →Openssl by Openssl
OpenSSL is a robust, commercial-grade toolkit for the Transport Layer Security (TLS) and Secure Sockets Layer (SSL) protocols. It provides cryptographic functions and is one of the most widely used libraries for implementing secure communications in applications worldwide.
Learn more about Openssl →Steel Belted Radius by Pulsesecure
⚠️ Risk & Real-World Impact
Worst Case
Remote code execution leading to complete system compromise, data theft, or persistent backdoor installation.
Likely Case
Denial of service through application crashes or memory corruption, potentially disrupting services.
If Mitigated
Limited impact with proper network segmentation, minimal exposure, and updated systems.
🎯 Exploit Status
Proof-of-concept code exists demonstrating the overflow. While weaponization is likely given the high CVSS score and remote nature, specific weaponized exploits may not be widely publicized.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: OpenSSL 1.0.1s, OpenSSL 1.0.2g
Vendor Advisory: https://www.openssl.org/news/secadv/20160301.txt
Restart Required: Yes
Instructions:
1. Identify affected OpenSSL versions using 'openssl version'. 2. Update OpenSSL packages through your distribution's package manager. 3. For Linux: 'sudo apt-get update && sudo apt-get upgrade openssl' (Debian/Ubuntu) or 'sudo yum update openssl' (RHEL/CentOS). 4. Restart services using OpenSSL. 5. Recompile statically linked applications with updated libraries.
🔧 Temporary Workarounds
Network filtering
allBlock or filter large ASN.1 data packets at network boundaries using firewalls or IPS systems.
Application input validation
allImplement input validation in applications to reject excessively long strings before passing to OpenSSL functions.
🧯 If You Can't Patch
- Isolate vulnerable systems in segmented network zones with strict access controls.
- Implement application-level firewalls or WAF rules to detect and block malicious payloads targeting this vulnerability.
🔍 How to Verify
Check if Vulnerable:
Run 'openssl version' and check if output shows 1.0.1 before 1.0.1s or 1.0.2 before 1.0.2g. Also check package manager for installed version.Check Version:
openssl versionVerify Fix Applied:
After patching, run 'openssl version' to confirm version is 1.0.1s or higher, or 1.0.2g or higher. Test applications that use OpenSSL for functionality.📡 Detection & Monitoring
Log Indicators:
- Application crashes with memory corruption errors
- Segmentation faults in OpenSSL-related processes
- Unusual memory usage patterns
Network Indicators:
- Large ASN.1 data packets sent to services using OpenSSL
- Unexpected connection attempts to SSL/TLS services
SIEM Query:
source="*" ("segmentation fault" OR "memory corruption" OR "buffer overflow") AND process="*openssl*" OR "*ssl*"🔗 References
- http://kb.juniper.net/InfoCenter/index?page=content&id=JSA10759
- http://lists.fedoraproject.org/pipermail/package-announce/2016-March/178358.html
- http://lists.fedoraproject.org/pipermail/package-announce/2016-March/178817.html
- http://lists.opensuse.org/opensuse-security-announce/2016-03/msg00001.html
- http://lists.opensuse.org/opensuse-security-announce/2016-03/msg00002.html
- http://lists.opensuse.org/opensuse-security-announce/2016-03/msg00003.html
- http://lists.opensuse.org/opensuse-security-announce/2016-03/msg00004.html
- http://lists.opensuse.org/opensuse-security-announce/2016-03/msg00006.html
- http://lists.opensuse.org/opensuse-security-announce/2016-03/msg00007.html
- http://lists.opensuse.org/opensuse-security-announce/2016-03/msg00009.html
- http://lists.opensuse.org/opensuse-security-announce/2016-03/msg00010.html
- http://lists.opensuse.org/opensuse-security-announce/2016-03/msg00011.html
- http://lists.opensuse.org/opensuse-security-announce/2016-03/msg00012.html
- http://lists.opensuse.org/opensuse-security-announce/2016-03/msg00017.html
- http://lists.opensuse.org/opensuse-security-announce/2016-03/msg00025.html
- http://lists.opensuse.org/opensuse-security-announce/2016-04/msg00038.html
- http://lists.opensuse.org/opensuse-security-announce/2016-05/msg00015.html
- http://lists.opensuse.org/opensuse-security-announce/2016-05/msg00017.html
- http://marc.info/?l=bugtraq&m=145983526810210&w=2
- http://marc.info/?l=bugtraq&m=146108058503441&w=2
- http://openssl.org/news/secadv/20160301.txt
- http://rhn.redhat.com/errata/RHSA-2016-0722.html
- http://rhn.redhat.com/errata/RHSA-2016-0996.html
- http://rhn.redhat.com/errata/RHSA-2016-2073.html
- http://rhn.redhat.com/errata/RHSA-2016-2957.html
- http://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20160302-openssl
- http://www.debian.org/security/2016/dsa-3500
- http://www.oracle.com/technetwork/security-advisory/cpuapr2016v3-2985753.html
- http://www.oracle.com/technetwork/security-advisory/cpujul2016-2881720.html
- http://www.oracle.com/technetwork/topics/security/bulletinapr2016-2952098.html
- http://www.oracle.com/technetwork/topics/security/bulletinjan2016-2867206.html
- http://www.oracle.com/technetwork/topics/security/linuxbulletinapr2016-2952096.html
- http://www.oracle.com/technetwork/topics/security/linuxbulletinjul2016-3090544.html
- http://www.oracle.com/technetwork/topics/security/ovmbulletinjul2016-3090546.html
- http://www.securityfocus.com/bid/83755
- http://www.securityfocus.com/bid/91787
- http://www.securitytracker.com/id/1035133
- http://www.ubuntu.com/usn/USN-2914-1
- https://cert-portal.siemens.com/productcert/pdf/ssa-412672.pdf
- https://git.openssl.org/?p=openssl.git%3Ba=commit%3Bh=578b956fe741bf8e84055547b1e83c28dd902c73
- https://h20566.www2.hpe.com/hpsc/doc/public/display?docLocale=en_US&docId=emr_na-hpesbhf03741en_us
- https://h20566.www2.hpe.com/portal/site/hpsc/public/kb/docDisplay?docId=emr_na-c05068681
- https://h20566.www2.hpe.com/portal/site/hpsc/public/kb/docDisplay?docId=emr_na-c05086877
- https://h20566.www2.hpe.com/portal/site/hpsc/public/kb/docDisplay?docId=emr_na-c05111017
- https://h20566.www2.hpe.com/portal/site/hpsc/public/kb/docDisplay?docId=emr_na-c05126404
- https://h20566.www2.hpe.com/portal/site/hpsc/public/kb/docDisplay?docId=emr_na-c05131085
- https://h20566.www2.hpe.com/portal/site/hpsc/public/kb/docDisplay?docId=emr_na-c05135617
- https://h20566.www2.hpe.com/portal/site/hpsc/public/kb/docDisplay?docId=emr_na-c05141441
- https://h20566.www2.hpe.com/portal/site/hpsc/public/kb/docDisplay?docId=emr_na-c05150736
- https://h20566.www2.hpe.com/portal/site/hpsc/public/kb/docDisplay?docId=emr_na-c05150800
- https://h20566.www2.hpe.com/portal/site/hpsc/public/kb/docDisplay?docId=emr_na-c05150888
- https://h20566.www2.hpe.com/portal/site/hpsc/public/kb/docDisplay?docId=emr_na-c05157667
- https://h20566.www2.hpe.com/portal/site/hpsc/public/kb/docDisplay?docId=emr_na-c05158380
- https://h20566.www2.hpe.com/portal/site/hpsc/public/kb/docDisplay?docId=emr_na-c05376917
- https://h20566.www2.hpe.com/portal/site/hpsc/public/kb/docDisplay?docId=emr_na-c05390722
- https://kb.pulsesecure.net/articles/Pulse_Security_Advisories/SA40168
- https://security.FreeBSD.org/advisories/FreeBSD-SA-16:12.openssl.asc
- https://security.gentoo.org/glsa/201603-15
- https://www.openssl.org/news/secadv/20160301.txt
- http://kb.juniper.net/InfoCenter/index?page=content&id=JSA10759
- http://lists.fedoraproject.org/pipermail/package-announce/2016-March/178358.html
- http://lists.fedoraproject.org/pipermail/package-announce/2016-March/178817.html
- http://lists.opensuse.org/opensuse-security-announce/2016-03/msg00001.html
- http://lists.opensuse.org/opensuse-security-announce/2016-03/msg00002.html
- http://lists.opensuse.org/opensuse-security-announce/2016-03/msg00003.html
- http://lists.opensuse.org/opensuse-security-announce/2016-03/msg00004.html
- http://lists.opensuse.org/opensuse-security-announce/2016-03/msg00006.html
- http://lists.opensuse.org/opensuse-security-announce/2016-03/msg00007.html
- http://lists.opensuse.org/opensuse-security-announce/2016-03/msg00009.html
- http://lists.opensuse.org/opensuse-security-announce/2016-03/msg00010.html
- http://lists.opensuse.org/opensuse-security-announce/2016-03/msg00011.html
- http://lists.opensuse.org/opensuse-security-announce/2016-03/msg00012.html
- http://lists.opensuse.org/opensuse-security-announce/2016-03/msg00017.html
- http://lists.opensuse.org/opensuse-security-announce/2016-03/msg00025.html
- http://lists.opensuse.org/opensuse-security-announce/2016-04/msg00038.html
- http://lists.opensuse.org/opensuse-security-announce/2016-05/msg00015.html
- http://lists.opensuse.org/opensuse-security-announce/2016-05/msg00017.html
- http://marc.info/?l=bugtraq&m=145983526810210&w=2
- http://marc.info/?l=bugtraq&m=146108058503441&w=2
- http://openssl.org/news/secadv/20160301.txt
- http://rhn.redhat.com/errata/RHSA-2016-0722.html
- http://rhn.redhat.com/errata/RHSA-2016-0996.html
- http://rhn.redhat.com/errata/RHSA-2016-2073.html
- http://rhn.redhat.com/errata/RHSA-2016-2957.html
- http://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20160302-openssl
- http://www.debian.org/security/2016/dsa-3500
- http://www.oracle.com/technetwork/security-advisory/cpuapr2016v3-2985753.html
- http://www.oracle.com/technetwork/security-advisory/cpujul2016-2881720.html
- http://www.oracle.com/technetwork/topics/security/bulletinapr2016-2952098.html
- http://www.oracle.com/technetwork/topics/security/bulletinjan2016-2867206.html
- http://www.oracle.com/technetwork/topics/security/linuxbulletinapr2016-2952096.html
- http://www.oracle.com/technetwork/topics/security/linuxbulletinjul2016-3090544.html
- http://www.oracle.com/technetwork/topics/security/ovmbulletinjul2016-3090546.html
- http://www.securityfocus.com/bid/83755
- http://www.securityfocus.com/bid/91787
- http://www.securitytracker.com/id/1035133
- http://www.ubuntu.com/usn/USN-2914-1
- https://cert-portal.siemens.com/productcert/pdf/ssa-412672.pdf
- https://git.openssl.org/?p=openssl.git%3Ba=commit%3Bh=578b956fe741bf8e84055547b1e83c28dd902c73
- https://h20566.www2.hpe.com/hpsc/doc/public/display?docLocale=en_US&docId=emr_na-hpesbhf03741en_us
- https://h20566.www2.hpe.com/portal/site/hpsc/public/kb/docDisplay?docId=emr_na-c05068681
- https://h20566.www2.hpe.com/portal/site/hpsc/public/kb/docDisplay?docId=emr_na-c05086877
- https://h20566.www2.hpe.com/portal/site/hpsc/public/kb/docDisplay?docId=emr_na-c05111017
- https://h20566.www2.hpe.com/portal/site/hpsc/public/kb/docDisplay?docId=emr_na-c05126404
- https://h20566.www2.hpe.com/portal/site/hpsc/public/kb/docDisplay?docId=emr_na-c05131085
- https://h20566.www2.hpe.com/portal/site/hpsc/public/kb/docDisplay?docId=emr_na-c05135617
- https://h20566.www2.hpe.com/portal/site/hpsc/public/kb/docDisplay?docId=emr_na-c05141441
- https://h20566.www2.hpe.com/portal/site/hpsc/public/kb/docDisplay?docId=emr_na-c05150736
- https://h20566.www2.hpe.com/portal/site/hpsc/public/kb/docDisplay?docId=emr_na-c05150800
- https://h20566.www2.hpe.com/portal/site/hpsc/public/kb/docDisplay?docId=emr_na-c05150888
- https://h20566.www2.hpe.com/portal/site/hpsc/public/kb/docDisplay?docId=emr_na-c05157667
- https://h20566.www2.hpe.com/portal/site/hpsc/public/kb/docDisplay?docId=emr_na-c05158380
- https://h20566.www2.hpe.com/portal/site/hpsc/public/kb/docDisplay?docId=emr_na-c05376917
- https://h20566.www2.hpe.com/portal/site/hpsc/public/kb/docDisplay?docId=emr_na-c05390722
- https://kb.pulsesecure.net/articles/Pulse_Security_Advisories/SA40168
- https://security.FreeBSD.org/advisories/FreeBSD-SA-16:12.openssl.asc
- https://security.gentoo.org/glsa/201603-15
- https://www.openssl.org/news/secadv/20160301.txt
