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Advisory severityHigh8.8Red Hat Linux

High [CVE-2026-56003] computeProps Property Buffer Heap Buffer Overflow

This high-severity Red Hat Linux advisory covers CVE-2026-56003 affecting Red Hat Enterprise Linux 10.0 Extended Update Support, Red Hat Enterprise Linux 7 Extended Lifecycle Support, Red Hat Enterprise Linux 8.4 Advanced Mission Critical Update Support.

Aggregated and source-linked by VulniPulse. Data sources, validation and limitations.

CVE-2026-56003 Source published Source updated

VulniPulse record published Record updated

CVE-2026-56003
Affected products & platforms
Red Hat LinuxRed Hat Enterprise Linux
Open source advisory

Summary

A heap buffer overflow due to missing size checking in the property buffer when parsing PCF files in libXfont2 ComputeScaledProperties() before libXfont2 before 2.0.8 could be used by attackers using authenticated X clients to execute code within the X server. 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.

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.

Red Hat severity: Important — CVSS 8.8 (CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H). Weakness: CWE-787.

Is CVE-2026-56003 exploited?

No exploitation is reported in the sources VulniPulse tracks: CVE-2026-56003 is not in the CISA KEV catalog (checked ) and this advisory does not report exploitation. That is not proof the vulnerability cannot be exploited.

How do I fix CVE-2026-56003?

Upgrade to a fixed release named by Red Hat:

  • libXfont2-0:2.0.6-5.el10_2.1
  • libXfont2-0:2.0.6-5.el10_0.1
  • libXfont2-0:2.0.3-2.el7_9
  • libXfont2-0:2.0.3-2.el8_10.1
  • libXfont2-0:2.0.3-2.el8_4.1
  • libXfont2-0:2.0.3-2.el8_6.1
  • libXfont2-0:2.0.3-2.el8_8.1
  • libXfont2-0:2.0.3-12.el9_8.1
  • libXfont2-0:2.0.3-12.el9_2.1
  • libXfont2-0:2.0.3-12.el9_4.1
  • libXfont2-0:2.0.3-12.el9_6.1
  • RHSA-2026:47079

10 more fixed releases are listed below.

Confirm against the vendor advisory before you patch.

Affected versions
  • < 2.0.8

Official advisory · high-confidence parse· fetched 3 days ago·verify at source

Fixed versions
  • libXfont2-0:2.0.6-5.el10_2.1
  • libXfont2-0:2.0.6-5.el10_0.1
  • libXfont2-0:2.0.3-2.el7_9
  • libXfont2-0:2.0.3-2.el8_10.1
  • libXfont2-0:2.0.3-2.el8_4.1
  • libXfont2-0:2.0.3-2.el8_6.1
  • libXfont2-0:2.0.3-2.el8_8.1
  • libXfont2-0:2.0.3-12.el9_8.1
  • libXfont2-0:2.0.3-12.el9_2.1
  • libXfont2-0:2.0.3-12.el9_4.1
  • libXfont2-0:2.0.3-12.el9_6.1
  • RHSA-2026:47079
  • RHSA-2026:51061
  • RHSA-2026:51063
  • RHSA-2026:47103
  • RHSA-2026:51060
  • RHSA-2026:51066
  • RHSA-2026:51067
  • RHSA-2026:47084
  • RHSA-2026:51062
  • RHSA-2026:51058
  • RHSA-2026:51059

Official advisory · high-confidence parse· fetched 3 days ago·verify at source

Mitigation checklist

Recommended fix / 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.

Official advisory · high-confidence parse· fetched 3 days ago·verify at source

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