CVE-2023-2953
📋 TL;DR
This vulnerability in OpenLDAP causes a null pointer dereference in the ber_memalloc_x() function, which can lead to denial of service (DoS) by crashing the LDAP service. Any system running vulnerable versions of OpenLDAP is affected, particularly LDAP servers and clients using the affected library.
💻 Affected Systems
- OpenLDAP
📦 What is this software?
Macos by Apple
macOS is Apple's desktop and laptop operating system powering Mac computers used by millions of professionals, developers, creative professionals, and enterprise users worldwide. Built on a Unix foundation with the Darwin kernel and modern Cocoa frameworks, macOS delivers a seamless ecosystem integr...
Learn more about Macos →Macos by Apple
macOS is Apple's desktop and laptop operating system powering Mac computers used by millions of professionals, developers, creative professionals, and enterprise users worldwide. Built on a Unix foundation with the Darwin kernel and modern Cocoa frameworks, macOS delivers a seamless ecosystem integr...
Learn more about Macos →Macos by Apple
macOS is Apple's desktop and laptop operating system powering Mac computers used by millions of professionals, developers, creative professionals, and enterprise users worldwide. Built on a Unix foundation with the Darwin kernel and modern Cocoa frameworks, macOS delivers a seamless ecosystem integr...
Learn more about Macos →Openldap by Openldap
⚠️ Risk & Real-World Impact
Worst Case
Complete LDAP service crash leading to denial of service, potentially disrupting authentication and directory services across an organization.
Likely Case
Service crash requiring manual restart, causing temporary authentication and directory lookup failures.
If Mitigated
Limited impact with proper monitoring and automated restart mechanisms in place.
🎯 Exploit Status
Exploitation requires sending specially crafted LDAP packets to trigger the null pointer dereference. Public proof-of-concept code exists in the disclosure references.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: OpenLDAP 2.6.4 and later
Vendor Advisory: https://bugs.openldap.org/show_bug.cgi?id=9904
Restart Required: Yes
Instructions:
1. Download OpenLDAP 2.6.4 or later from openldap.org. 2. Stop the LDAP service. 3. Install the updated version. 4. Restart the LDAP service. 5. Verify the service is running correctly.
🔧 Temporary Workarounds
Network filtering
linuxBlock or filter malicious LDAP packets at network perimeter
iptables -A INPUT -p tcp --dport 389 -m string --string "malicious_pattern" --algo bm -j DROP
Rate limiting
linuxLimit LDAP connection rates to reduce DoS impact
iptables -A INPUT -p tcp --dport 389 -m limit --limit 10/min --limit-burst 20 -j ACCEPT
🧯 If You Can't Patch
- Implement network segmentation to isolate LDAP servers from untrusted networks
- Deploy monitoring and automated restart scripts to minimize service disruption
🔍 How to Verify
Check if Vulnerable:
Check OpenLDAP version with: slapd -V 2>&1 | grep '^@'Check Version:
slapd -V 2>&1 | head -5Verify Fix Applied:
Verify version is 2.6.4 or higher: slapd -V 2>&1 | grep '2.6.[4-9]\|2.[7-9]'📡 Detection & Monitoring
Log Indicators:
- LDAP service crash logs
- Segmentation fault errors in system logs
- Unexpected slapd process termination
Network Indicators:
- Unusual LDAP packet patterns
- Multiple connection attempts to LDAP port 389
SIEM Query:
source="ldap.log" AND ("segmentation fault" OR "null pointer" OR "crash")🔗 References
- http://seclists.org/fulldisclosure/2023/Jul/47
- http://seclists.org/fulldisclosure/2023/Jul/48
- http://seclists.org/fulldisclosure/2023/Jul/52
- https://access.redhat.com/security/cve/CVE-2023-2953
- https://bugs.openldap.org/show_bug.cgi?id=9904
- https://security.netapp.com/advisory/ntap-20230703-0005/
- https://support.apple.com/kb/HT213843
- https://support.apple.com/kb/HT213844
- https://support.apple.com/kb/HT213845
- http://seclists.org/fulldisclosure/2023/Jul/47
- http://seclists.org/fulldisclosure/2023/Jul/48
- http://seclists.org/fulldisclosure/2023/Jul/52
- https://access.redhat.com/security/cve/CVE-2023-2953
- https://bugs.openldap.org/show_bug.cgi?id=9904
- https://security.netapp.com/advisory/ntap-20230703-0005/
- https://support.apple.com/kb/HT213843
- https://support.apple.com/kb/HT213844
- https://support.apple.com/kb/HT213845
