CVE-2026-50256
Published: June 6, 2026Last modified: June 8, 2026
Description
A stack-based buffer overflow flaw was found in the X.Org X server and Xwayland. A mismatch between the X server and the libXfont2 library's maximum font name length can cause a stack buffer overflow during font alias resolution. The server allocates a 256 byte stack buffer but libXfont2's alias target name length is 1024 bytes. A font alias name between 257 and 1023 bytes causes the X server to copy that name into the undersized stack buffer without further checks. This may be used to crash the server, or for privilege escalation if the X server runs as root.
Severity score breakdown
| Parameter | Value |
|---|---|
| Base score | 7.8 |
| Attack Vector | LOCAL |
| Attack complexity | LOW |
| Privileges required | LOW |
| User interaction | NONE |
| Scope | UNCHANGED |
| Confidentiality | HIGH |
| Integrity impact | HIGH |
| Availability impact | HIGH |
| Vector | CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H |
Status
| Product | Release | Package | Status |
|---|---|---|---|
| Alpaquita Linux | 23 LTS | xorg-server | Fixed (21.1.23-r0) |
| 25 LTS | xorg-server | Fixed (21.1.23-r0) | |
| Stream | xorg-server | Fixed (21.1.23-r0) |
References
- https://access.redhat.com/errata/RHSA-2026:26562
- https://access.redhat.com/errata/RHSA-2026:26590
- https://access.redhat.com/errata/RHSA-2026:26610
- https://access.redhat.com/errata/RHSA-2026:26709
- https://access.redhat.com/security/cve/CVE-2026-50256
- https://bugzilla.redhat.com/show_bug.cgi?id=2485380
- https://gitlab.freedesktop.org/xorg/xserver/-/commit/bb5158f962dc935e58ef8b4b5fcb31be201a6e07
- https://lists.x.org/archives/xorg-announce/2026-June/003702.html
- https://redhat.atlassian.net/browse/PSIRTSUPT-16950