8.5

CVE-2026-55999: x.org x_server Heap-based Buffer Overflow

CVSS: 8.5v3.1HighAnalyzed
AliasesSUSE-SU-2026:2792-1RHSA-2026:38486RHSA-2026:38487
Published 08-07-2026Last modified 09-07-2026
Open JSON

Vulnerability summary

CVE-2026-55999 is a high (CVSS 8.5) Heap-based Buffer Overflow vulnerability in x.org x_server. EPSS estimates a 0.33% chance of exploitation in the next 30 days, higher than 25% of scored vulnerabilities.

Overall risk
34/100
0100
Medium · default modelHow is this calculated?
CVSS score
8.5/10
010
High · v3.1 (CVE.org)
EPSS score
0.33%
0%100%
Low · +0.06 pp in 30 days
KEVNot listedIn no KEV catalog
RansomwareNone recordedNo known use recorded
Public exploits0No public exploits recorded

Advisory lineage

Upstream 0 · Downstream 16 · Related 11
MGASA-2026-0303OPENSUSE-SU-2026:11227-1OPENSUSE-SU-2026:11244-1OPENSUSE-SU-2026:21273-1OPENSUSE-SU-2026:21283-1RHSA-2026:38489

Timeline

  1. 08-07-2026
    PublishedVulnerability first disclosed.
  2. 09-07-2026
    Last modifiedVulnerability information updated.

Description

Local attackers with a X connection able to provide PCX fonts to the X server xorg-server before 21.2.24 and xwayland before 24.1.13 could cause a heap buffer overflow via SetFont due to missing glyph boundary checks.

CVSS metrics

7 scores · 7 sources · 1 version

EPSS trend

Probability

0.33%

Chance of exploitation in the next 30 days

Percentile

25%

Versus all other CVEs

30-day change

+0.06 pp

From 0.27% on 19-09-2026

19-09-202619-10-2026
EPSS score
0.33%

Known exploited

Compare KEV catalogs

Not in any of the 3 tracked catalogs.

Public exploits

0 found

No public exploits indexed.

Weaknesses

CWE · root cause

Affected systems

Redhat19 products
  • xorg-x11-server< 0:1.20.11-34.el9_8.3 | < 0:1.20.11-28.el8_10.3 | < 0:1.20.11-21.el9_2.1 | < 0:1.20.11-29.el9_4.1 | < 0:1.20.11-8.el8_6.1 | < 0:1.20.10-5.el8_4.1 | < 0:1.20.11-34.el9_6.1 | < 0:1.20.11-19.el8_8.1 | < 0:1.20.4-36.el7_9
  • xorg-x11-server-common< 0:1.20.11-34.el9_8.3 | < 0:1.20.11-28.el8_10.3 | < 0:1.20.11-21.el9_2.1 | < 0:1.20.11-29.el9_4.1 | < 0:1.20.11-8.el8_6.1 | < 0:1.20.10-5.el8_4.1 | < 0:1.20.11-34.el9_6.1 | < 0:1.20.11-19.el8_8.1 | < 0:1.20.4-36.el7_9
  • xorg-x11-server-debuginfo< 0:1.20.11-34.el9_8.3 | < 0:1.20.11-28.el8_10.3 | < 0:1.20.11-21.el9_2.1 | < 0:1.20.11-29.el9_4.1 | < 0:1.20.11-8.el8_6.1 | < 0:1.20.10-5.el8_4.1 | < 0:1.20.11-34.el9_6.1 | < 0:1.20.11-19.el8_8.1 | < 0:1.20.4-36.el7_9
  • xorg-x11-server-debugsource< 0:1.20.11-34.el9_8.3 | < 0:1.20.11-28.el8_10.3 | < 0:1.20.11-21.el9_2.1 | < 0:1.20.11-29.el9_4.1 | < 0:1.20.11-8.el8_6.1 | < 0:1.20.10-5.el8_4.1 | < 0:1.20.11-34.el9_6.1 | < 0:1.20.11-19.el8_8.1
  • xorg-x11-server-devel< 0:1.20.11-34.el9_8.3 | < 0:1.20.11-28.el8_10.3 | < 0:1.20.11-34.el9_6.1 | < 0:1.20.4-36.el7_9
Ubuntu4 products
  • xorg-serverAll versions (No fix recorded)
  • xorg-server-hwe-16.04All versions (No fix recorded)
  • xorg-server-hwe-18.04All versions (No fix recorded)
  • xwaylandAll versions (No fix recorded)
X.org3 products
Debian2 products
  • xorg-serverAll versions (No fix recorded) | < 2:21.1.16-1.3+deb13u4 | < 2:21.1.24-1
  • xwaylandAll versions (No fix recorded) | < 2:24.1.13-1
Suse2 products
  • xorg-x11-server&distro=SUSE Linux Enterprise Server 12 SP5-LTSS< 1.19.6-10.105.1
  • xorg-x11-server&distro=SUSE Linux Enterprise Server LTSS Extended Security 12 SP5< 1.19.6-10.105.1
Chainguard1 product
  • xorg-server< 21.1.24-r0
Wolfi1 product
  • xorg-server< 21.1.24-r0

7 vendors · 32 products

References

40 links
Show all 40 references