CVE-2015-6420
📋 TL;DR
This vulnerability allows remote attackers to execute arbitrary commands on affected Cisco devices by sending crafted serialized Java objects. It affects numerous Cisco product lines including networking, collaboration, security, and wireless devices. The issue stems from insecure deserialization in Apache Commons Collections library components.
💻 Affected Systems
- Cisco Collaboration and Social Media
- Cisco Endpoint Clients and Client Software
- Cisco Network Application, Service, and Acceleration
- Cisco Network and Content Security Devices
- Cisco Network Management and Provisioning
- Cisco Routing and Switching - Enterprise and Service Provider
- Cisco Unified Computing
- Cisco Voice and Unified Communications Devices
- Cisco Video, Streaming, TelePresence, and Transcoding Devices
- Cisco Wireless
- Cisco Hosted Services
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Complete system compromise with remote code execution, allowing attackers to gain full control of affected devices, steal sensitive data, pivot to internal networks, or deploy ransomware.
Likely Case
Remote code execution leading to data theft, network reconnaissance, or installation of backdoors for persistent access.
If Mitigated
Limited impact through network segmentation, proper access controls, and monitoring that detects exploitation attempts.
🎯 Exploit Status
Multiple public exploits exist for Java deserialization vulnerabilities. The vulnerability is actively exploited in the wild.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Varies by product - see Cisco Security Advisory
Vendor Advisory: http://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20151209-java-deserialization
Restart Required: Yes
Instructions:
1. Review Cisco Security Advisory for affected products. 2. Identify specific patches for your devices. 3. Apply patches during maintenance window. 4. Restart affected services or devices as required.
🔧 Temporary Workarounds
Network Segmentation
allIsolate affected devices from untrusted networks and limit access to trusted sources only.
Access Control Lists
allImplement strict ACLs to limit which IP addresses can communicate with vulnerable services.
🧯 If You Can't Patch
- Implement network segmentation to isolate vulnerable devices
- Deploy intrusion detection/prevention systems to monitor for exploitation attempts
🔍 How to Verify
Check if Vulnerable:
Check device version against Cisco Security Advisory. Use vulnerability scanners that detect CVE-2015-6420.Check Version:
show version (Cisco IOS/IOS XE) or show version detail (NX-OS)Verify Fix Applied:
Verify patch installation and check that device version matches patched version in advisory.📡 Detection & Monitoring
Log Indicators:
- Java deserialization errors
- Unexpected process execution
- Unusual network connections from device
Network Indicators:
- Serialized Java objects in network traffic to vulnerable ports
- Unexpected outbound connections from affected devices
SIEM Query:
source="cisco-device" AND (event_type="java_error" OR process="unexpected_executable")🔗 References
- http://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20151209-java-deserialization
- http://www.oracle.com/technetwork/security-advisory/cpujul2018-4258247.html
- http://www.securityfocus.com/bid/78872
- 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://lists.apache.org/thread.html/r352e40ca9874d1beb4ad95403792adca7eb295e6bc3bd7b65fabcc21%40%3Ccommits.samza.apache.org%3E
- https://www.kb.cert.org/vuls/id/581311
- https://www.tenable.com/security/research/tra-2017-14
- https://www.tenable.com/security/research/tra-2017-23
- http://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20151209-java-deserialization
- http://www.oracle.com/technetwork/security-advisory/cpujul2018-4258247.html
- http://www.securityfocus.com/bid/78872
- https://foxglovesecurity.com/2015/11/06/what-do-weblogic-websphere-jboss-jenkins-opennms-and-your-application-have-in-common-this-vulnerability/
- 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://lists.apache.org/thread.html/r352e40ca9874d1beb4ad95403792adca7eb295e6bc3bd7b65fabcc21%40%3Ccommits.samza.apache.org%3E
- https://news.apache.org/foundation/entry/apache_commons_statement_to_widespread
- https://www.kb.cert.org/vuls/id/576313
- https://www.kb.cert.org/vuls/id/581311
- https://www.tenable.com/security/research/tra-2017-14
- https://www.tenable.com/security/research/tra-2017-23
