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 | 2026-06-30 03:20:45 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 0.052870000 (date 2026-07-03)
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
Attack Vector
LocalAttack Complexity
LowPrivileges Required
LowUser Interaction
NoneScope
UnchangedConfidentiality
HighIntegrity
HighAvailability
HighCVSS: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
| Source | Vendor | Product | Version | Platforms |
|---|---|---|---|---|
| CNA | Red Hat | Red Hat Enterprise Linux 10 | unaffected 0:24.1.9-4.el10_2.2 * rpm | Not specified |
| CNA | Red Hat | Red Hat Enterprise Linux 8 | unaffected 0:21.1.3-20.el8_10.2 * rpm | Not specified |
| CNA | Red Hat | Red Hat Enterprise Linux 8 | unaffected 0:1.20.11-28.el8_10.2 * rpm | Not specified |
| CNA | Red Hat | Red Hat Enterprise Linux 8 | unaffected 0:1.15.0-10.el8_10 * rpm | Not specified |
| CNA | Red Hat | Red Hat Enterprise Linux 9 | unaffected 0:24.1.9-4.el9_8.2 * rpm | Not specified |
| CNA | Red Hat | Red Hat Enterprise Linux 9 | unaffected 0:1.20.11-34.el9_8.2 * rpm | Not specified |
| CNA | Red Hat | Red Hat Enterprise Linux 9 | unaffected 0:1.15.0-7.el9_8.2 * rpm | Not specified |
| CNA | Red Hat | Red Hat Enterprise Linux 6 | Not specified | Not specified |
| CNA | Red Hat | Red Hat Enterprise Linux 6 | Not specified | Not specified |
| CNA | Red Hat | Red Hat Enterprise Linux 7 | Not specified | Not specified |
| CNA | Red Hat | Red Hat Enterprise Linux 7 | Not specified | Not specified |
| ADP | Red Hat | Red Hat Enterprise Linux AppStream V. 10 | Not specified | Not specified |
| ADP | Red Hat | Red Hat Enterprise Linux AppStream V. 8 | Not specified | Not specified |
| ADP | Red Hat | Red Hat Enterprise Linux AppStream V. 9 | Not specified | Not specified |
| ADP | Red Hat | Red Hat Enterprise Linux CodeReady Linux Builder V. 10 | Not specified | Not specified |
| ADP | Red Hat | Red Hat Enterprise Linux CRB V. 8 | Not specified | Not specified |
| ADP | Red Hat | Red Hat Enterprise Linux CodeReady Linux Builder V. 9 | Not specified | Not specified |
| ADP | Red Hat | Red Hat Enterprise Linux 6 | Not specified | Not specified |
| ADP | Red Hat | Red Hat Enterprise Linux 7 | Not specified | Not specified |
References
| Reference | Source | Link | Tags |
|---|---|---|---|
| access.redhat.com/errata/RHSA-2026:26562 | 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 |
| 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 | |
| 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 | |
| redhat.atlassian.net/browse/PSIRTSUPT-16950 | [email protected] | redhat.atlassian.net | Permissions Required |
| 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-2026:26566 | 0b0ca135-0b70-47e7-9f44-1890c2a1c46c | access.redhat.com | |
| access.redhat.com/errata/RHSA-2026:26610 | 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-2026:26566: 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-2026:29844: 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)
There are currently no legacy QID mappings associated with this CVE.