Vulnerability · Published Jul 8, 2026 · Assigned by suse
CVE-2026-55999xorg-server / xwayland glamor font atlas Heap Buffer Overflow
High 8.5
In plain English
A high-severity heap buffer overflow in xorg-server from X.Org. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.3% (higher than 27% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.
Severity (CVSS 3.1)8.5High
Exploit odds (30 days)0.3%top 73.3% of all CVEs
Exploited in the wildNo reportsCISA SSVC: none
Attack toolingNoneno public tooling known
Official 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.
Affected packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| AlmaLinux:8 | xorg-x11-server-Xdmx | 1.20.11-28.el8_10.3 | ALSA-2026:38487 |
| AlmaLinux:9 | xorg-x11-server-Xdmx | 1.20.11-34.el9_8.3 | ALSA-2026:38486 |
| AlmaLinux:8 | xorg-x11-server-Xephyr | 1.20.11-28.el8_10.3 | ALSA-2026:38487 |
| AlmaLinux:9 | xorg-x11-server-Xephyr | 1.20.11-34.el9_8.3 | ALSA-2026:38486 |
| AlmaLinux:8 | xorg-x11-server-Xnest | 1.20.11-28.el8_10.3 | ALSA-2026:38487 |
| AlmaLinux:9 | xorg-x11-server-Xnest | 1.20.11-34.el9_8.3 | ALSA-2026:38486 |
| AlmaLinux:8 | xorg-x11-server-Xorg | 1.20.11-28.el8_10.3 | ALSA-2026:38487 |
| AlmaLinux:9 | xorg-x11-server-Xorg | 1.20.11-34.el9_8.3 | ALSA-2026:38486 |
| AlmaLinux:8 | xorg-x11-server-Xvfb | 1.20.11-28.el8_10.3 | ALSA-2026:38487 |
| AlmaLinux:9 | xorg-x11-server-Xvfb | 1.20.11-34.el9_8.3 | ALSA-2026:38486 |
| AlmaLinux:10 | xorg-x11-server-Xwayland | 24.1.9-4.el10_2.3 | ALSA-2026:38489 |
| AlmaLinux:8 | xorg-x11-server-Xwayland | 21.1.3-20.el8_10.3 | ALSA-2026:38488 |
| AlmaLinux:9 | xorg-x11-server-Xwayland | 24.1.9-4.el9_8.3 | ALSA-2026:38490 |
| AlmaLinux:10 | xorg-x11-server-Xwayland-devel | 24.1.9-4.el10_2.3 | ALSA-2026:38489 |
| AlmaLinux:9 | xorg-x11-server-Xwayland-devel | 24.1.9-4.el9_8.3 | ALSA-2026:38490 |
| AlmaLinux:8 | xorg-x11-server-common | 1.20.11-28.el8_10.3 | ALSA-2026:38487 |
| AlmaLinux:9 | xorg-x11-server-common | 1.20.11-34.el9_8.3 | ALSA-2026:38486 |
| AlmaLinux:8 | xorg-x11-server-devel | 1.20.11-28.el8_10.3 | ALSA-2026:38487 |
| AlmaLinux:9 | xorg-x11-server-devel | 1.20.11-34.el9_8.3 | ALSA-2026:38486 |
| AlmaLinux:8 | xorg-x11-server-source | 1.20.11-28.el8_10.3 | ALSA-2026:38487 |
| AlmaLinux:9 | xorg-x11-server-source | 1.20.11-34.el9_8.3 | ALSA-2026:38486 |
| Alpine:v3.24 | xorg-server | 21.1.24-r0 | ALPINE-CVE-2026-55999 |
| Alpine:v3.24 | xwayland | 24.1.13-r0 | ALPINE-CVE-2026-55999 |
| Debian:12 | xorg-server | no fix listed | DEBIAN-CVE-2026-55999 |
| Debian:13 | xorg-server | 2:21.1.16-1.3+deb13u4 | DEBIAN-CVE-2026-55999 |
| Debian:14 | xorg-server | 2:21.1.24-1 | DEBIAN-CVE-2026-55999 |
| Debian:12 | xwayland | no fix listed | DEBIAN-CVE-2026-55999 |
| Debian:13 | xwayland | no fix listed | DEBIAN-CVE-2026-55999 |
| Debian:14 | xwayland | 2:24.1.13-1 | DEBIAN-CVE-2026-55999 |
| Rocky Linux:8 | xorg-x11-server | 0:1.20.11-28.el8_10.3 | RLSA-2026:38487 |
| Rocky Linux:9 | xorg-x11-server | 0:1.20.11-34.el9_8.3 | RLSA-2026:38486 |
| Rocky Linux:10 | xorg-x11-server-Xwayland | 0:24.1.9-4.el10_2.3 | RLSA-2026:38489 |
| Rocky Linux:8 | xorg-x11-server-Xwayland | 0:21.1.3-20.el8_10.3 | RLSA-2026:38488 |
| Rocky Linux:9 | xorg-x11-server-Xwayland | 0:24.1.9-4.el9_8.3 | RLSA-2026:38490 |
| Ubuntu:22.04:LTS | xorg-server | no fix listed | UBUNTU-CVE-2026-55999 |
| Ubuntu:24.04:LTS | xorg-server | no fix listed | UBUNTU-CVE-2026-55999 |
| Ubuntu:25.10 | xorg-server | no fix listed | UBUNTU-CVE-2026-55999 |
| Ubuntu:26.04:LTS | xorg-server | no fix listed | UBUNTU-CVE-2026-55999 |
| Ubuntu:26.10 | xorg-server | no fix listed | UBUNTU-CVE-2026-55999 |
| Ubuntu:22.04:LTS | xwayland | no fix listed | UBUNTU-CVE-2026-55999 |
| Ubuntu:24.04:LTS | xwayland | no fix listed | UBUNTU-CVE-2026-55999 |
| Ubuntu:25.10 | xwayland | no fix listed | UBUNTU-CVE-2026-55999 |
| Ubuntu:26.04:LTS | xwayland | no fix listed | UBUNTU-CVE-2026-55999 |
| Ubuntu:26.10 | xwayland | no fix listed | UBUNTU-CVE-2026-55999 |
Affected products (as reported)
| Vendor | Product | Versions |
|---|---|---|
| X.Org | xorg-server | 0 – before 21.1.24 |
| X.Org | xwayland | 0 – before 24.1.13 |
Weakness: CWE-122 · Vector: CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:C/C:H/I:H/A:H