Xorg-x11-server: xorg-x11-server-xwayland: xorg-x11-server: stack buffer overflow in font alias resolution due to libxfont2 name length mismatch
Summary
| CVE | CVE-2026-50256 |
|---|---|
| State | PUBLISHED |
| Assigner | redhat |
| Source Priority | CVE Program / NVD first with legacy fallback |
| Published | 2026-06-05 12:16:38 UTC |
| Updated | 2026-11-04 23:17:40 UTC |
| 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. |
Risk And Classification
Primary CVSS: v3.1 7.8 HIGH from ADP
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
EPSS: 0.001570000 probability, percentile 0.049190000 (date 2026-11-04)
Problem Types: CWE-121 | CWE-121 Stack-based Buffer Overflow
| Version | Source | Type | Score | Severity | Vector |
|---|---|---|---|---|---|
| 3.1 | ADP | CVSS | 7.8 | HIGH | CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H |
| 3.1 | [email protected] | Secondary | 7.8 | HIGH | CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H |
| 3.1 | 0b0ca135-0b70-47e7-9f44-1890c2a1c46c | Secondary | 7.8 | HIGH | CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H |
| 3.1 | CNA | CVSS | 7.8 | HIGH | CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H |
CVSS v3.1 Breakdown
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
NVD Known Affected Configurations (CPE 2.3)
| Type | Vendor | Product | Version | Update | Edition | Language |
|---|---|---|---|---|---|---|
| Operating System | Redhat | Enterprise Linux | 10.0 | All | All | All |
| Operating System | Redhat | Enterprise Linux | 7.0 | All | All | All |
| Operating System | Redhat | Enterprise Linux | 8.0 | All | All | All |
| Operating System | Redhat | Enterprise Linux | 9.0 | All | All | All |
| Application | X.org | Xwayland | All | All | All | All |
| Application | X.org | X Server | All | All | All | All |
Vendor Declared Affected Products
References
| Reference | Source | Link | Tags |
|---|---|---|---|
| access.redhat.com/errata/RHSA-2026:36798 | 0b0ca135-0b70-47e7-9f44-1890c2a1c46c | access.redhat.com | |
| access.redhat.com/errata/RHSA-2026:36792 | 0b0ca135-0b70-47e7-9f44-1890c2a1c46c | access.redhat.com | |
| access.redhat.com/errata/RHSA-2026:26562 | 0b0ca135-0b70-47e7-9f44-1890c2a1c46c | access.redhat.com | |
| access.redhat.com/errata/RHSA-2026:46456 | 0b0ca135-0b70-47e7-9f44-1890c2a1c46c | access.redhat.com | |
| access.redhat.com/errata/RHSA-2026:38502 | 0b0ca135-0b70-47e7-9f44-1890c2a1c46c | access.redhat.com | |
| access.redhat.com/errata/RHSA-2026:36768 | 0b0ca135-0b70-47e7-9f44-1890c2a1c46c | access.redhat.com | |
| access.redhat.com/security/cve/CVE-2026-50256 | 0b0ca135-0b70-47e7-9f44-1890c2a1c46c | access.redhat.com | Vendor Advisory |
| access.redhat.com/errata/RHSA-2026:36633 | 0b0ca135-0b70-47e7-9f44-1890c2a1c46c | access.redhat.com | |
| lists.x.org/archives/xorg-announce/2026-June/003702.html | [email protected] | lists.x.org | Mailing List, Third Party Advisory |
| gitlab.freedesktop.org/xorg/xserver/-/commit/bb5158f962dc935e58ef8b4b5fcb31be201a6e07 | [email protected] | gitlab.freedesktop.org | Patch |
| access.redhat.com/errata/RHSA-2026:28923 | 0b0ca135-0b70-47e7-9f44-1890c2a1c46c | access.redhat.com | |
| access.redhat.com/errata/RHSA-2026:26590 | 0b0ca135-0b70-47e7-9f44-1890c2a1c46c | access.redhat.com | |
| access.redhat.com/errata/RHSA-2026:36634 | 0b0ca135-0b70-47e7-9f44-1890c2a1c46c | access.redhat.com | |
| bugzilla.redhat.com/show_bug.cgi | 0b0ca135-0b70-47e7-9f44-1890c2a1c46c | bugzilla.redhat.com | Issue Tracking, Vendor Advisory |
| access.redhat.com/errata/RHSA-2026:29844 | 0b0ca135-0b70-47e7-9f44-1890c2a1c46c | access.redhat.com | |
| access.redhat.com/errata/RHSA-2026:26709 | 0b0ca135-0b70-47e7-9f44-1890c2a1c46c | access.redhat.com | |
| access.redhat.com/errata/RHSA-2026:46460 | 0b0ca135-0b70-47e7-9f44-1890c2a1c46c | access.redhat.com | |
| access.redhat.com/errata/RHSA-2026:36083 | 0b0ca135-0b70-47e7-9f44-1890c2a1c46c | access.redhat.com | |
| access.redhat.com/errata/RHSA-2026:49519 | 0b0ca135-0b70-47e7-9f44-1890c2a1c46c | access.redhat.com | |
| access.redhat.com/errata/RHSA-2026:36086 | 0b0ca135-0b70-47e7-9f44-1890c2a1c46c | access.redhat.com | |
| access.redhat.com/errata/RHSA-2026:46473 | 0b0ca135-0b70-47e7-9f44-1890c2a1c46c | access.redhat.com | |
| access.redhat.com/errata/RHSA-2026:46382 | 0b0ca135-0b70-47e7-9f44-1890c2a1c46c | access.redhat.com | |
| redhat.atlassian.net/browse/PSIRTSUPT-16950 | [email protected] | redhat.atlassian.net | Permissions Required |
| access.redhat.com/errata/RHSA-2026:36087 | 0b0ca135-0b70-47e7-9f44-1890c2a1c46c | access.redhat.com | |
| access.redhat.com/errata/RHSA-2026:38810 | 0b0ca135-0b70-47e7-9f44-1890c2a1c46c | access.redhat.com | |
| access.redhat.com/errata/RHSA-2026:36791 | 0b0ca135-0b70-47e7-9f44-1890c2a1c46c | access.redhat.com | |
| access.redhat.com/errata/RHSA-2026:46377 | 0b0ca135-0b70-47e7-9f44-1890c2a1c46c | access.redhat.com | |
| security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-50256.json | 0b0ca135-0b70-47e7-9f44-1890c2a1c46c | security.access.redhat.com | |
| access.redhat.com/errata/RHSA-2026:36085 | 0b0ca135-0b70-47e7-9f44-1890c2a1c46c | access.redhat.com | |
| access.redhat.com/errata/RHSA-2026:26566 | 0b0ca135-0b70-47e7-9f44-1890c2a1c46c | access.redhat.com | |
| access.redhat.com/errata/RHSA-2026:46392 | 0b0ca135-0b70-47e7-9f44-1890c2a1c46c | access.redhat.com | |
| access.redhat.com/errata/RHSA-2026:26610 | 0b0ca135-0b70-47e7-9f44-1890c2a1c46c | access.redhat.com | |
| access.redhat.com/errata/RHSA-2026:36632 | 0b0ca135-0b70-47e7-9f44-1890c2a1c46c | access.redhat.com | |
| access.redhat.com/errata/RHSA-2026:46385 | 0b0ca135-0b70-47e7-9f44-1890c2a1c46c | access.redhat.com | |
| CVE Program record | CVE.ORG | www.cve.org | canonical |
| NVD vulnerability detail | NVD | nvd.nist.gov | canonical, analysis |
Vendor Comments And Credit
Discovery Credit
CNA: Upstream acknowledges Anonymous (Trend Micro Zero Day Initiative) as the original reporter. (en)
Additional Advisory Data
| Source | Time | Event |
|---|---|---|
| CNA | 2026-05-15T03:14:46.000Z | Reported to Red Hat. |
| CNA | 2026-06-02T00:00:00.000Z | Made public. |
| ADP | 2026-05-15T03:14:46.000Z | Reported to Red Hat. |
| ADP | 2026-06-02T00:00:00.000Z | Made public. |
Solutions
ADP: RHSA-2026:49519: Red Hat Enterprise Linux Server -EXTENSION(v. 6 ELS-EXTENSION), Red Hat Enterprise Linux Server Optional -EXTENSION (v. 6 ELS -EXTENSION)
ADP: RHSA-2026:46473: Red Hat Enterprise Linux Server (v. 7 ELS), Red Hat Enterprise Linux Server Optional (v. 7 ELS)
ADP: RHSA-2026:36083: Red Hat Enterprise Linux Server (v. 7 ELS), Red Hat Enterprise Linux Server Optional (v. 7 ELS)
ADP: RHSA-2026:36798: Red Hat Enterprise Linux AppStream EUS (v. 10.0), Red Hat Enterprise Linux CodeReady Linux Builder EUS (v. 10.0)
ADP: RHSA-2026:26566: Red Hat Enterprise Linux AppStream (v. 10), Red Hat Enterprise Linux CodeReady Linux Builder (v. 10)
ADP: RHSA-2026:28923: Red Hat Enterprise Linux AppStream (v. 8)
ADP: RHSA-2026:26709: Red Hat Enterprise Linux AppStream (v. 8), Red Hat Enterprise Linux CRB (v. 8)
ADP: RHSA-2026:26562: Red Hat Enterprise Linux AppStream (v. 8)
ADP: RHSA-2026:46382: Red Hat Enterprise Linux AppStream AUS (v.8.4), Red Hat Enterprise Linux AppStream EUS EXTENSION (v.8.4)
ADP: RHSA-2026:36792: Red Hat Enterprise Linux AppStream AUS (v.8.4), Red Hat Enterprise Linux AppStream EUS EXTENSION (v.8.4)
ADP: RHSA-2026:46460: Red Hat Enterprise Linux AppStream AUS (v.8.6), Red Hat Enterprise Linux AppStream EUS EXTENSION (v.8.6)
ADP: RHSA-2026:36791: Red Hat Enterprise Linux AppStream AUS (v.8.6), Red Hat Enterprise Linux AppStream EUS EXTENSION (v.8.6)
ADP: RHSA-2026:38810: Red Hat Enterprise Linux AppStream AUS (v.8.6), Red Hat Enterprise Linux AppStream EUS EXTENSION (v.8.6)
ADP: RHSA-2026:46385: Red Hat Enterprise Linux AppStream E4S (v.8.8), Red Hat Enterprise Linux AppStream TUS (v.8.8)
ADP: RHSA-2026:36768: Red Hat Enterprise Linux AppStream E4S (v.8.8), Red Hat Enterprise Linux AppStream TUS (v.8.8)
ADP: RHSA-2026:38502: Red Hat Enterprise Linux AppStream E4S (v.8.8), Red Hat Enterprise Linux AppStream TUS (v.8.8)
ADP: RHSA-2026:46377: Red Hat Enterprise Linux AppStream E4S (v.9.2)
ADP: RHSA-2026:36086: Red Hat Enterprise Linux AppStream E4S (v.9.2)
ADP: RHSA-2026:36633: Red Hat Enterprise Linux AppStream E4S (v.9.2)
ADP: RHSA-2026:46456: Red Hat Enterprise Linux AppStream E4S (v.9.4)
ADP: RHSA-2026:36087: Red Hat Enterprise Linux AppStream E4S (v.9.4)
ADP: RHSA-2026:36632: Red Hat Enterprise Linux AppStream E4S (v.9.4)
ADP: RHSA-2026:46392: Red Hat Enterprise Linux AppStream EUS (v.9.6)
ADP: RHSA-2026:36085: Red Hat CodeReady Linux Builder EUS (v.9.6), Red Hat Enterprise Linux AppStream EUS (v.9.6)
ADP: RHSA-2026:36634: Red Hat CodeReady Linux Builder EUS (v.9.6), Red Hat Enterprise Linux AppStream EUS (v.9.6)
ADP: RHSA-2026:29844: Red Hat Enterprise Linux AppStream (v. 9)
ADP: RHSA-2026:26610: Red Hat Enterprise Linux AppStream (v. 9), Red Hat Enterprise Linux CodeReady Linux Builder (v. 9)
ADP: RHSA-2026:26590: Red Hat Enterprise Linux AppStream (v. 9), Red Hat Enterprise Linux CodeReady Linux Builder (v. 9)
Workarounds
CNA: 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.