CVE-2023-6246
📋 TL;DR
A heap-based buffer overflow in glibc's syslog functions allows attackers to crash applications or potentially escalate privileges locally. This affects programs using syslog/vsyslog without proper openlog initialization when the program name exceeds 1024 bytes. Systems running glibc 2.36 or newer are vulnerable.
💻 Affected Systems
- glibc (GNU C Library)
📦 What is this software?
Fedora by Fedoraproject
Fedora by Fedoraproject
Glibc by Gnu
The GNU C Library (glibc) is the core C library for Linux systems, providing essential system calls and basic functions for all C programs. It is a fundamental component that nearly every Linux application depends on.
Learn more about Glibc →⚠️ Risk & Real-World Impact
Worst Case
Local privilege escalation to root, allowing complete system compromise.
Likely Case
Application crash leading to denial of service.
If Mitigated
No impact if programs properly call openlog with non-NULL ident or have short program names.
🎯 Exploit Status
Exploitation requires local access and specific program conditions. Proof-of-concept code is publicly available.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: glibc 2.39 or distributions' backported patches
Vendor Advisory: https://access.redhat.com/security/cve/CVE-2023-6246
Restart Required: Yes
Instructions:
1. Update glibc via your distribution's package manager. 2. For Red Hat/CentOS: yum update glibc. 3. For Debian/Ubuntu: apt update && apt upgrade libc6. 4. Restart affected services or reboot system.
🔧 Temporary Workarounds
Ensure openlog is called
linuxModify applications to call openlog with non-NULL ident before using syslog/vsyslog.
Limit program name length
linuxEnsure argv[0] basename is less than 1024 bytes for vulnerable programs.
🧯 If You Can't Patch
- Restrict local access to vulnerable systems using strict user permissions.
- Monitor for suspicious syslog activity and application crashes.
🔍 How to Verify
Check if Vulnerable:
Check glibc version: ldd --version | head -1. If version is 2.36 or higher, check if any applications use syslog without proper openlog calls.Check Version:
ldd --version | head -1Verify Fix Applied:
Verify glibc version is patched: ldd --version | head -1. Check distribution security advisories for patch confirmation.📡 Detection & Monitoring
Log Indicators:
- Application crashes with segmentation faults in syslog functions
- Unusual syslog activity patterns
Network Indicators:
- None - local exploitation only
SIEM Query:
search 'segmentation fault' AND 'syslog' OR 'vsyslog' in application logs🔗 References
- http://packetstormsecurity.com/files/176931/glibc-qsort-Out-Of-Bounds-Read-Write.html
- http://packetstormsecurity.com/files/176932/glibc-syslog-Heap-Based-Buffer-Overflow.html
- http://seclists.org/fulldisclosure/2024/Feb/3
- http://seclists.org/fulldisclosure/2024/Feb/5
- https://access.redhat.com/security/cve/CVE-2023-6246
- https://bugzilla.redhat.com/show_bug.cgi?id=2249053
- https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/D2FIH77VHY3KCRROCXOT6L27WMZXSJ2G/
- https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/MWQ6BZJ6CV5UAW4VZSKJ6TO4KIW2KWAQ/
- https://security.gentoo.org/glsa/202402-01
- https://security.netapp.com/advisory/ntap-20240216-0007/
- https://www.openwall.com/lists/oss-security/2024/01/30/6
- https://www.qualys.com/2024/01/30/cve-2023-6246/syslog.txt
- http://packetstormsecurity.com/files/176931/glibc-qsort-Out-Of-Bounds-Read-Write.html
- http://packetstormsecurity.com/files/176932/glibc-syslog-Heap-Based-Buffer-Overflow.html
- http://seclists.org/fulldisclosure/2024/Feb/3
- http://seclists.org/fulldisclosure/2024/Feb/5
- https://access.redhat.com/security/cve/CVE-2023-6246
- https://bugzilla.redhat.com/show_bug.cgi?id=2249053
- https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/D2FIH77VHY3KCRROCXOT6L27WMZXSJ2G/
- https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/MWQ6BZJ6CV5UAW4VZSKJ6TO4KIW2KWAQ/
- https://security.gentoo.org/glsa/202402-01
- https://security.netapp.com/advisory/ntap-20240216-0007/
- https://www.openwall.com/lists/oss-security/2024/01/30/6
- https://www.qualys.com/2024/01/30/cve-2023-6246/syslog.txt
