CVE-2025-8058: GNU C Library Buffer Overflow Vulnerability

CVE-2025-8058 Overview

CVE-2025-8058 is a Double Free vulnerability affecting the regcomp function in the GNU C library (glibc) versions 2.4 through 2.41. The vulnerability occurs when a previous memory allocation fails during regex compilation, either due to a natural malloc failure or through an interposed malloc that injects random failures. This double free condition can allow buffer manipulation depending on how the regex pattern is constructed, potentially leading to memory corruption and system instability.

Critical Impact

A successful exploitation of this double free vulnerability could allow attackers to manipulate memory buffers, potentially leading to arbitrary code execution or denial of service on systems running affected glibc versions across all supported architectures and ABIs.

Affected Products

• GNU C Library (glibc) versions 2.4 through 2.41
• All architectures and ABIs supported by glibc
• Linux distributions using affected glibc versions

Discovery Timeline

• 2025-07-23 - CVE-2025-8058 published to NVD
• 2025-11-04 - Last updated in NVD database

Technical Details for CVE-2025-8058

Vulnerability Analysis

The regcomp function in glibc is responsible for compiling POSIX regular expressions into an internal representation that can be used by regexec for pattern matching. This vulnerability (CWE-415: Double Free) arises from improper memory management when allocation failures occur during the compilation process.

When a memory allocation operation fails within the regex compilation workflow, the error handling code path attempts to free memory resources that may have already been freed or were never successfully allocated. This creates a double free condition where the same memory region is passed to free() twice.

The attack surface requires local access and involves triggering specific memory allocation failure conditions. An attacker could potentially exploit this by crafting specific regex patterns combined with memory pressure conditions, or by using an interposed malloc implementation that deliberately injects allocation failures at strategic points.

Root Cause

The root cause lies in the error handling logic within regcomp that fails to properly track which memory allocations have succeeded and which have failed. When an allocation fails partway through the compilation process, the cleanup code does not correctly account for the state of previously allocated memory blocks, leading to double free conditions.

The issue affects the fundamental regex compilation infrastructure in glibc, making it relevant across all architectures and ABI configurations that use these regex functions.

Attack Vector

The attack vector is local, requiring the attacker to have the ability to influence regex compilation on the target system. Exploitation scenarios include:

• Applications that compile user-supplied regular expressions where memory conditions can be influenced
• Systems under memory pressure where natural malloc failures may occur during regex operations
• Environments where a malicious interposed malloc library can inject controlled failures

The double free can lead to heap corruption, where freed memory chunks become corrupted or point to unexpected memory locations. Depending on the regex construction and heap layout, this could potentially be leveraged for further memory manipulation.

For technical details on the vulnerability mechanism and the specific code paths involved, see the Sourceware Bug Report #33185 and the Openwall OSS Security Discussion.

Detection Methods for CVE-2025-8058

Indicators of Compromise

• Unexpected application crashes or segmentation faults in processes using regex operations
• Double free error messages in system logs from memory debugging tools (ASAN, valgrind)
• Anomalous memory allocation patterns in applications performing regex compilation
• Core dumps indicating heap corruption in glibc regex-related functions

Detection Strategies

• Monitor for processes crashing with heap corruption signatures in regcomp or related regex functions
• Deploy memory sanitizers (AddressSanitizer) in development and testing environments to detect double free conditions
• Implement log analysis for malloc/free debugging output indicating double-free attempts
• Use runtime detection tools that can identify memory management violations in glibc functions

Monitoring Recommendations

• Enable crash reporting and core dump analysis on systems running applications with user-supplied regex processing
• Monitor system memory utilization patterns for unusual behavior that could indicate exploitation attempts
• Track glibc version deployment across infrastructure to identify vulnerable systems
• Implement application-level monitoring for regex compilation failures and error rates

How to Mitigate CVE-2025-8058

Immediate Actions Required

• Update glibc to the patched version (post-2.41 with the security fix applied)
• Identify all systems running glibc versions 2.4 through 2.41
• Prioritize patching on systems that process untrusted regex patterns
• Review applications that compile user-supplied regular expressions

Patch Information

The GNU C Library maintainers have addressed this vulnerability through a commit to the glibc repository. The fix corrects the memory management logic in the regex compilation error handling path to prevent double free conditions.

The patch is available in the glibc Git repository with commit hash 3ff17af18c38727b88d9115e536c069e6b5d601f. System administrators should update to a glibc version that includes this fix or apply the patch directly if building from source.

Additional technical discussion and context can be found in the Sourceware Bug Report #33185.

Workarounds

• Limit regex compilation to trusted input sources where possible
• Implement input validation and length limits on regex patterns before compilation
• Use alternative regex libraries (such as PCRE2) for applications requiring user-supplied patterns until patching is complete
• Deploy memory monitoring tools to detect and terminate processes exhibiting double free behavior

# Check current glibc version on the system
ldd --version

# Example: Verify glibc version and determine if patching is required
# Systems running glibc 2.4 through 2.41 should be prioritized for updates
rpm -q glibc || dpkg -l libc6 | grep libc6