CVE-2023-2602: Libcap pthread_create() DOS Vulnerability

CVE-2023-2602 Overview

A memory leak vulnerability was discovered in the pthread_create() function within libcap, a library for getting and setting POSIX.1e capabilities on Linux systems. This issue allows a malicious actor to cause __real_pthread_create() to return an error, which can lead to process memory exhaustion. The vulnerability is classified as CWE-401 (Missing Release of Memory after Effective Lifetime).

Critical Impact
Local attackers with limited privileges can exploit this memory leak vulnerability to exhaust process memory, potentially causing denial of service conditions on systems using the affected libcap library.

Affected Products

libcap_project libcap (version 2.66)
Red Hat Enterprise Linux (versions 6.0, 7.0, 8.0, 9.0)
Debian Linux (versions 10.0, 11.0, 12.0)
Fedora (versions 37, 38)

Discovery Timeline

2023-06-06 - CVE-2023-2602 published to NVD
2024-11-21 - Last updated in NVD database

Technical Details for CVE-2023-2602

Vulnerability Analysis

The vulnerability exists within the pthread_create() wrapper function in libcap. When certain error conditions are triggered during thread creation, the __real_pthread_create() function can return an error without properly releasing allocated memory resources. This missing cleanup path creates a memory leak that accumulates over time.

The issue was identified during a comprehensive code review conducted by X41 D-Sec as part of an OSTIF-funded security audit. The local attack vector requires the attacker to have low-level privileges on the system, but no user interaction is needed to trigger the vulnerability.

Root Cause

The root cause is a missing memory release mechanism (CWE-401) in the error handling path of the pthread_create() function wrapper. When the underlying __real_pthread_create() call fails and returns an error, previously allocated memory is not properly freed before the function returns. This creates a gradual memory leak that can be repeatedly triggered to exhaust available process memory.

Attack Vector

The attack vector is local, requiring the attacker to execute code on the target system. The attacker can repeatedly trigger the error condition in pthread_create() to cause memory exhaustion over time. While the impact is limited to availability (denial of service) rather than confidentiality or integrity compromise, it can affect system stability for applications relying on the affected libcap versions.

The vulnerability requires:

Local access to the system
Low privilege level (standard user)
The ability to execute code that calls the vulnerable pthread_create() wrapper function
Repeated invocation to cause meaningful memory exhaustion

Detection Methods for CVE-2023-2602

Indicators of Compromise

Unusual memory growth in processes using libcap for capability management
Repeated thread creation failures logged by applications using libcap
System performance degradation due to memory pressure from affected processes
Out-of-memory (OOM) killer activity targeting processes linked against libcap

Detection Strategies

Monitor process memory usage for applications utilizing libcap functionality
Implement memory leak detection tools (such as Valgrind or AddressSanitizer) during application testing
Review system logs for repeated pthread_create() failures
Use system monitoring to track memory consumption trends over time

Monitoring Recommendations

Deploy SentinelOne agents to monitor for abnormal memory consumption patterns in Linux environments
Configure memory usage alerts for critical applications using libcap
Establish baseline memory profiles for processes and alert on significant deviations
Monitor for repeated denial of service attempts targeting local system resources

How to Mitigate CVE-2023-2602

Immediate Actions Required

Inventory all systems running affected versions of libcap (version 2.66 and potentially others)
Prioritize patching systems running Red Hat Enterprise Linux 6.0-9.0, Debian Linux 10.0-12.0, or Fedora 37-38
Review applications that depend on libcap for capability management
Apply vendor-provided security updates as they become available

Patch Information

Security updates addressing this vulnerability are available through the respective Linux distribution package managers. Red Hat has tracked this issue in Bug Report #2209114. Fedora users should apply updates announced through the Fedora Package Announcement mailing list.

Administrators should update libcap packages using their distribution's standard package management commands to obtain the patched version that properly handles memory deallocation in the error path.

Workarounds

Limit local access to systems running vulnerable libcap versions until patching is complete
Monitor and set memory limits for processes using libcap via cgroups or ulimit configurations
Consider temporarily disabling or restricting applications that heavily utilize the affected pthread_create wrapper
Implement process restart policies for critical services to mitigate memory exhaustion impact

bash

# Check installed libcap version on RPM-based systems
rpm -q libcap

# Check installed libcap version on Debian-based systems
dpkg -l | grep libcap

# Update libcap on Red Hat/CentOS/Fedora
sudo dnf update libcap

# Update libcap on Debian/Ubuntu
sudo apt update && sudo apt upgrade libcap2