CVE-2023-0687: GNU Glibc Buffer Overflow Vulnerability

CVE-2023-0687 Overview

A buffer overflow vulnerability has been identified in GNU C Library (glibc) version 2.38. This vulnerability affects the __monstartup function within the gmon.c file, which is part of the Call Graph Monitor component used for program profiling. When exploited, the vulnerability could allow an attacker to trigger a buffer overflow condition through manipulation of function inputs.

Critical Impact

Buffer overflow in glibc's profiling component could potentially lead to arbitrary code execution, memory corruption, or denial of service on affected systems. However, exploitation requires the target application to be compiled with gmon profiling enabled and involves inputs that are generally trusted addresses of the running application.

Affected Products

• GNU C Library (glibc) 2.38
• Applications compiled with gmon profiling enabled using affected glibc versions
• Linux distributions using vulnerable glibc versions

Discovery Timeline

• 2023-02-06 - CVE-2023-0687 published to NVD
• 2024-11-21 - Last updated in NVD database

Technical Details for CVE-2023-0687

Vulnerability Analysis

The vulnerability resides in the __monstartup function within gmon.c, which is responsible for initializing the Call Graph Monitor profiling system. The function contains insufficient bounds checking when processing memory addresses, leading to a classic buffer overflow condition (CWE-120: Buffer Copy without Checking Size of Input).

It is important to note that the real-world exploitability of this vulnerability is disputed. The inputs that trigger this vulnerability are essentially addresses of the running application built with gmon profiling enabled. These inputs are typically trusted or would require a separate security flaw to be controlled by an attacker.

The vulnerability can potentially be exploited remotely without requiring authentication or user interaction. However, practical exploitation scenarios are limited due to the nature of the affected component and the requirement for gmon profiling to be enabled at compile time.

Root Cause

The root cause is a buffer overflow vulnerability in the __monstartup function of gmon.c. The function fails to properly validate the size of input data before copying it into fixed-size memory buffers. This allows data to overflow beyond allocated buffer boundaries, potentially corrupting adjacent memory regions or overwriting critical program data structures.

Attack Vector

The attack vector involves manipulating the input parameters passed to the __monstartup function during profiling initialization. The function accepts memory address ranges for setting up the call graph profiling, and improper validation of these addresses can lead to buffer overflow conditions.

The vulnerability occurs in the following context:

1. An application must be compiled with gmon profiling enabled (-pg flag)
2. The profiling system initializes via __monstartup at program startup
3. Malformed or manipulated address parameters can trigger the buffer overflow
4. This could potentially allow memory corruption or code execution

Since no verified proof-of-concept code is publicly available, the specific exploitation methodology remains theoretical. For technical implementation details, refer to the Sourceware Bug Report.

Detection Methods for CVE-2023-0687

Indicators of Compromise

• Unusual crashes or segmentation faults in applications compiled with gmon profiling
• Unexpected memory access violations in profiling-enabled binaries
• Anomalous behavior during application startup in gmon-instrumented programs

Detection Strategies

• Monitor for applications compiled with the -pg profiling flag that may be exposed to untrusted inputs
• Implement memory protection mechanisms such as ASLR, stack canaries, and NX bit enforcement
• Use memory safety tools like AddressSanitizer (ASan) during development and testing to detect buffer overflows

Monitoring Recommendations

• Audit systems for applications built with gmon profiling enabled in production environments
• Review glibc version deployed across infrastructure to identify vulnerable installations
• Monitor system logs for crash reports and core dumps that may indicate exploitation attempts

How to Mitigate CVE-2023-0687

Immediate Actions Required

• Identify all applications compiled with gmon profiling (-pg flag) in production environments
• Consider disabling gmon profiling in production builds unless specifically required for performance analysis
• Apply the available patch from the glibc project to affected systems
• Upgrade to patched versions of glibc when available from your distribution vendor

Patch Information

A patch has been submitted to address this vulnerability. The patch is available through the GLIBC Patch Submission on the glibc patchwork system. Organizations should monitor their Linux distribution's package repositories for updated glibc packages that incorporate this fix.

Additional technical details and discussion can be found in the Sourceware Bug Report.

Workarounds

• Recompile applications without the -pg profiling flag for production deployments
• Implement additional memory protection mechanisms at the OS level (ASLR, DEP/NX)
• Restrict access to profiling-enabled binaries to trusted users only
• Consider using alternative profiling tools that don't rely on gmon instrumentation

# Configuration example
# Verify if an application was compiled with gmon profiling
nm /path/to/binary | grep -E "(__monstartup|_mcount|__gmon_start__)"

# Recompile without profiling (remove -pg flag)
gcc -o application source.c  # Omit -pg flag for production builds

# Check glibc version on your system
ldd --version