fontconfig up to 2.17.0 FcFontCapabilities fcfreetype.c off-by-one

CVSS Meta Temp Score
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CTI Interest Score
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6.3$0-$5k0.29

Summaryinfo

A vulnerability, which was classified as problematic, has been found in fontconfig up to 2.17.0. Affected by this vulnerability is an unknown functionality of the file fcfreetype.c of the component FcFontCapabilities. This manipulation causes off-by-one. This vulnerability is handled as CVE-2026-34085. It is possible to launch the attack on the local host. There is not any exploit available. It is advisable to upgrade the affected component.

Detailsinfo

A vulnerability was found in fontconfig up to 2.17.0. It has been declared as problematic. Affected by this vulnerability is an unknown functionality of the file fcfreetype.c of the component FcFontCapabilities. The manipulation with an unknown input leads to a off-by-one vulnerability. The CWE definition for the vulnerability is CWE-193. A product calculates or uses an incorrect maximum or minimum value that is 1 more, or 1 less, than the correct value. As an impact it is known to affect confidentiality, integrity, and availability. The summary by CVE is:

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.

The advisory is shared at gitlab.freedesktop.org. This vulnerability is known as CVE-2026-34085 since 03/25/2026. The exploitation appears to be easy. An attack has to be approached locally. Technical details are known, but no exploit is available.

The vulnerability scanner Nessus provides a plugin with the ID 303838 (Linux Distros Unpatched Vulnerability : CVE-2026-34085), which helps to determine the existence of the flaw in a target environment.

Upgrading to version 2.17.1 eliminates this vulnerability. Applying the patch b9bec06d73340f1b5727302d13ac3df307b7febc is able to eliminate this problem. The bugfix is ready for download at gitlab.freedesktop.org. The best possible mitigation is suggested to be upgrading to the latest version.

The vulnerability is also documented in the vulnerability database at Tenable (303838). Several companies clearly confirm that VulDB is the primary source for best vulnerability data.

Productinfo

Name

Version

CPE 2.3info

CPE 2.2info

CVSSv4info

VulDB Vector: 🔒
VulDB Reliability: 🔍

CVSSv3info

VulDB Meta Base Score: 6.3
VulDB Meta Temp Score: 6.3

VulDB Base Score: 5.3
VulDB Temp Score: 5.1
VulDB Vector: 🔒
VulDB Reliability: 🔍

NVD Base Score: 7.8
NVD Vector: 🔒

CNA Base Score: 5.9
CNA Vector (MITRE): 🔒

CVSSv2info

AVACAuCIA
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VectorComplexityAuthenticationConfidentialityIntegrityAvailability
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VulDB Base Score: 🔒
VulDB Temp Score: 🔒
VulDB Reliability: 🔍

Exploitinginfo

Class: Off-by-one
CWE: CWE-193 / CWE-189
CAPEC: 🔒
ATT&CK: 🔒

Physical: Partially
Local: Yes
Remote: No

Availability: 🔒
Status: Not defined

EPSS Score: 🔒
EPSS Percentile: 🔒

Price Prediction: 🔍
Current Price Estimation: 🔒

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Nessus ID: 303838
Nessus Name: Linux Distros Unpatched Vulnerability : CVE-2026-34085

Threat Intelligenceinfo

Interest: 🔍
Active Actors: 🔍
Active APT Groups: 🔍

Countermeasuresinfo

Recommended: Upgrade
Status: 🔍

0-Day Time: 🔒

Upgrade: fontconfig 2.17.1
Patch: b9bec06d73340f1b5727302d13ac3df307b7febc

Timelineinfo

03/25/2026 Advisory disclosed
03/25/2026 +0 days CVE reserved
03/25/2026 +0 days VulDB entry created
04/01/2026 +7 days VulDB entry last update

Sourcesinfo

Advisory: b9bec06d73340f1b5727302d13ac3df307b7febc
Status: Confirmed

CVE: CVE-2026-34085 (🔒)
GCVE (CVE): GCVE-0-2026-34085
GCVE (VulDB): GCVE-100-353221

Entryinfo

Created: 03/25/2026 18:42
Updated: 04/01/2026 11:59
Changes: 03/25/2026 18:42 (66), 03/26/2026 22:05 (2), 04/01/2026 11:59 (12)
Complete: 🔍
Cache ID: 216:8C0:103

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