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CVE-2026-34085

Quick assessment

Affected
fontconfig project fontconfig
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

fontconfig是freedesktop开源的一种与字体相关的计算机程序库。 fontconfig 2.17.1之前版本存在安全漏洞，该漏洞源于sfnt能力处理期间分配存在差一错误，可能导致一字节越界写入，进而引发崩溃或代码执行。

CVSS 5.9 · Medium EPSS 0.18% · P7

Possible ATT&CK Techniques 1 AI

T1203 · Exploitation for Client Execution
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I. Basic Information for CVE-2026-34085

Vulnerability Information
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Vulnerability Title
N/A
Source: CVE Program / CVE List V5
Vulnerability 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.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:L
Source: CVE Program / CVE List V5
Vulnerability Type
Off-by-one错误
Source: CVE Program / CVE List V5
Vulnerability Title
fontconfig 安全漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
fontconfig是freedesktop开源的一种与字体相关的计算机程序库。 fontconfig 2.17.1之前版本存在安全漏洞，该漏洞源于sfnt能力处理期间分配存在差一错误，可能导致一字节越界写入，进而引发崩溃或代码执行。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
fontconfig project fontconfig 0 ~ 2.17.1 -

II. Public POCs for CVE-2026-34085

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III. Intelligence Information for CVE-2026-34085

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Patches & Fixes for CVE-2026-34085 (2)

Other References for CVE-2026-34085 (1)

IV. Related Vulnerabilities

Same weakness: CWE-193

V. Comments for CVE-2026-34085

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