# CVE-2026-34085: fontconfig before 2.17.1 has an off-by-one error in allocation during sfnt capability handling, leading to a one-byte out-of-bounds write, and potentially a crash or code execution. This is in FcFontCapabilities in fcfreetype.c.

CVE-2026-34085 is fixed in fontconfig on 1 platform by DEBIAN-CVE-2026-34085 (version 2.17.1-3), released March 25, 2026. It is not reported as exploited. Patch Radar priority: Routine.

- Web page: https://patchblox.com/security/cve/CVE-2026-34085
- Priority: Routine
- CVSS: 5.9 (Moderate)
- EPSS: 0.0013
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Published: Mar 25, 2026
- Weakness: Off-by-one Error
- Vendor advisory: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-34085

## Description

fontconfig before 2.17.1 has an off-by-one error in allocation during sfnt capability handling, leading to a one-byte out-of-bounds write, and potentially a crash or code execution. This is in FcFontCapabilities in fcfreetype.c.

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Linux | fontconfig Debian 14 | 2.17.1-3 | [DEBIAN-CVE-2026-34085](https://patchblox.com/security/data/fix/linux/debian-cve-2026-34085.md) | Mar 25, 2026 |

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Data as of 2026-11-08T06:59:42Z UTC. Source: Patchblox Patch Radar (https://patchblox.com/security/patch-radar). Patchblox finds out-of-date software on Windows, macOS and Linux and updates it through release rings: https://patchblox.com/demo

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