CVE-2026-56003
Description
A flaw was found in libXfont2. This vulnerability allows an attacker to achieve arbitrary code execution or cause a Denial of Service (DoS) by providing a specially crafted Portable Compiled Format (PCF) font file. Due to missing bounds checks when processing font properties in the ComputeScaledProperties function, duplicate property entries can overflow a fixed-size heap buffer, leading to memory corruption.
Statement
This vulnerability is rated as having an Important impact because a local authenticated user or X client can exploit memory corruption within processes utilizing libXfont2 to potentially execute arbitrary code or trigger a denial of service. By supplying crafted Portable Compiled Format (PCF) font data containing redundant property entries, the library writes beyond allocated buffer bounds during font property calculations. Headless servers and systems operating without active graphical display servers do not expose this functionality and are not affected.
Mitigation
Mitigation for this issue is either not available or the currently available options do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base, or stability.
Common Vulnerability Scoring System (CVSS) Score Details
Info alert:Important note
CVSS scores for open source components depend on vendor-specific factors (e.g. version or build chain). Therefore, Red Hat's score and impact rating can be different from NVD and other vendors. Red Hat remains the authoritative CVE Naming Authority (CNA) source for its products and services (see Red Hat classifications).
CVSS v3 Score Breakdown
| Red Hat | NVD | cve.org | |
|---|---|---|---|
| Base Score | 8.8 | 8.8 | 8.5 |
| Attack Vector | Network | Network | Network |
| Attack Complexity | Low | Low | High |
| Privileges Required | Low | Low | Low |
| User Interaction | None | None | None |
| Scope | Unchanged | Unchanged | Changed |
| Confidentiality | High | High | High |
| Integrity Impact | High | High | High |
| Availability Impact | High | High | High |
Vector
Red Hat: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
NVD: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
cve.org: CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:C/C:H/I:H/A:H
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