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.

Routine

CVSS

5.9

Moderate

Exploitation

None reported

No vendor assessment

CISA KEV

Not listed

Not in the Known Exploited Vulnerabilities catalog

EPSS

0.0013

2nd percentile

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

Product	Fixed in	Fix	Released
Linux
fontconfig · Debian 14	2.17.1-3	DEBIAN-CVE-2026-34085	Mar 25, 2026

Details

Published
March 25, 2026
Weakness
Off-by-one Error
CVSS vector
CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:L
Vendor advisory
https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-34085

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