CVE-2025-15536: BYVoid OpenCC Buffer Overflow Vulnerability

CVE-2025-15536 Overview

A heap-based buffer overflow vulnerability has been identified in BYVoid OpenCC, an open-source Chinese text conversion library. This vulnerability affects the opencc::MaxMatchSegmentation function within the file src/MaxMatchSegmentation.cpp in versions up to and including 1.1.9. When exploited, improper memory handling allows an attacker to trigger a heap-based buffer overflow condition through specially crafted input.

Critical Impact
Local attackers with low privileges can exploit this heap-based buffer overflow to potentially corrupt memory, cause application crashes, or achieve limited compromise of confidentiality, integrity, and availability on systems running vulnerable OpenCC versions.

Affected Products

BYVoid OpenCC versions up to 1.1.9
Applications and libraries that integrate OpenCC for Chinese text conversion
Systems using vulnerable OpenCC builds for text processing workflows

Discovery Timeline

January 18, 2026 - CVE-2025-15536 published to NVD
January 20, 2026 - Last updated in NVD database

Technical Details for CVE-2025-15536

Vulnerability Analysis

This vulnerability is classified under CWE-119 (Improper Restriction of Operations within the Bounds of a Memory Buffer). The flaw resides in the opencc::MaxMatchSegmentation function, which is responsible for segmenting Chinese text using a maximum matching algorithm. During text processing operations, the function fails to properly validate buffer boundaries, resulting in heap memory being written beyond allocated bounds.

The attack requires local access to the target system and low-level privileges to execute. While the exploit has been made publicly available, the local attack vector limits the scope of potential attacks. Successful exploitation could lead to limited impacts on confidentiality, integrity, and availability of the affected system.

Root Cause

The root cause of this vulnerability stems from insufficient bounds checking within the MaxMatchSegmentation.cpp implementation. The segmentation algorithm processes input text without adequately verifying that write operations remain within the allocated heap buffer boundaries. This oversight allows malformed or specially crafted input to trigger out-of-bounds memory writes, corrupting adjacent heap memory regions.

Attack Vector

The attack vector is local, meaning an attacker must have existing access to the system running the vulnerable OpenCC library. The attacker would need to supply malicious input to an application utilizing OpenCC's text conversion functionality. The exploit has been publicly disclosed, providing potential attackers with a reproducible method to trigger the vulnerability.

Technical details about the vulnerability mechanism can be found in the GitHub Issue Discussion and the reproducible example published by the security researcher.

Detection Methods for CVE-2025-15536

Indicators of Compromise

Unexpected application crashes or segmentation faults in processes using OpenCC library
Abnormal memory allocation patterns or heap corruption errors in OpenCC-dependent applications
Core dumps containing evidence of heap overflow in MaxMatchSegmentation.cpp code paths

Detection Strategies

Monitor applications using OpenCC for unexpected terminations or memory-related exceptions
Implement memory sanitizers (ASan, MSan) in development and testing environments to detect heap overflows
Review application logs for error messages related to OpenCC text processing failures
Deploy endpoint detection solutions capable of identifying heap overflow exploitation attempts

Monitoring Recommendations

Enable crash reporting and analysis for applications integrating OpenCC library
Implement file integrity monitoring on OpenCC library files to detect unauthorized modifications
Monitor system logs for unusual process behavior in applications performing Chinese text conversion
Configure SentinelOne agents to alert on memory corruption indicators in protected processes

How to Mitigate CVE-2025-15536

Immediate Actions Required

Update BYVoid OpenCC to a patched version that includes commit 345c9a50ab07018f1b4439776bad78a0d40778ec
Audit applications and systems using OpenCC to identify vulnerable deployments
Restrict local access to systems running vulnerable OpenCC versions to trusted users only
Consider temporarily disabling OpenCC functionality in critical applications until patching is complete

Patch Information

A fix has been committed to the OpenCC repository. The patch is identified by commit hash 345c9a50ab07018f1b4439776bad78a0d40778ec. Organizations should apply this patch by either updating to a version that includes this commit or by manually applying the fix to their OpenCC installation.

For detailed patch information, refer to the GitHub Commit Details and the GitHub Pull Request.

Workarounds

Implement input validation and sanitization before passing data to OpenCC functions
Run OpenCC-dependent applications in sandboxed or containerized environments to limit impact of exploitation
Apply memory protection mechanisms such as ASLR and DEP/NX to reduce exploitability
Restrict file system and network access for processes using the vulnerable library

bash

# Verify OpenCC version and check for vulnerable installations
opencc --version

# Check if the patch commit is present in your installation
cd /path/to/opencc/source
git log --oneline | grep 345c9a50ab07018f1b4439776bad78a0d40778ec

# Rebuild OpenCC from patched source
git pull origin main
mkdir build && cd build
cmake ..
make && sudo make install