Red Hat Enterprise Linux 10: Stack-based Buffer Overflow
CVE-2026-50259 is a high-severity stack-based buffer overflow vulnerability in Red Hat Enterprise Linux 10 from Red Hat, with a CVSS 3.1 base score of 7.8 out of 10. It can be exploited with local access to the system by an attacker with a low-privileged account, without any action from a user. There is no confirmed exploitation so far. EPSS estimates a 0.17% chance of exploitation within 30 days, which is low compared with other CVEs.
High severity with no evidence of exploitation so far.
What to do
- Update X Server to 21.1.23 or a later version.
- Update Xwayland to 24.1.12 or a later version.
- Read the advisory on redhat.atlassian.net for workarounds and exact fixed builds.
Affected products and versions
Version data comes from the organisation that assigned the CVE. Confirm against the vendor advisory before deciding you are unaffected.
How the severity score breaks down
- Attack vector
- LocalThe attacker needs local access or must trick a user into running something.
- Attack complexity
- LowNo special conditions are needed; the attack works reliably.
- Privileges required
- LowA basic user account is enough.
- User interaction
- NoneNo action by a victim is required.
- Scope
- UnchangedImpact stays within the vulnerable component.
- Confidentiality
- HighAll data handled by the component can be read.
- Integrity
- HighData or code can be modified at will.
- Availability
- HighThe component can be taken down completely.
Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H. Scored by CNA (redhat.com).
| Scoring system | Score | Severity | Scored by |
|---|---|---|---|
| CVSS 3.1 | 7.8 | High | CNA (redhat.com) |
| CVSS 3.1 | 7.8 | High | CNA |
Official description
A stack-based buffer overflow flaw was found in the X.Org X server and Xwayland. _XkbSetMapChecks() declares a fixed-size stack buffer mapWidths[256] indexed by key type index. The helper function CheckKeyTypes() writes to this buffer at a client-controlled offset, allowing a stack buffer overflow. This may be used to crash the server, or for privilege escalation if the X server runs as root.
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
The underlying weakness: Stack-based Buffer Overflow
The product writes past the end of a buffer that was allocated on the stack.
How developers prevent this class of flaw
- Use automatic buffer overflow detection mechanisms that are offered by certain compilers or compiler extensions. Examples include: the Microsoft Visual Studio /GS flag, Fedora/Red Hat FORTIFY_SOURCE GCC flag, StackGuard, and ProPolice, which provide various mechanisms including canary-based detection and range/index checking. D3-SFCV (Stack Frame Canary Validation) from D3FEND discusses canary-based detection in detail.
- Use an abstraction library to abstract away risky APIs. Not a complete solution.
- Implement and perform bounds checking on input.
Timeline
- CVE record published.
- CISA published its SSVC assessment (exploitation: none, automatable: no, technical impact: total).
- Record last changed materially (score, affected products, status or references).
References
Advisories
- redhat.atlassian.net/browse/PSIRTSUPT-16950Permissions Required
Patches and release notes
Third-party and government advisories
- access.redhat.com/security/cve/CVE-2026-50259Third Party Advisory
- bugzilla.redhat.com/show_bug.cgi?id=2485384Issue Tracking, Third Party Advisory
- lists.x.org/archives/xorg-announce/2026-June/003702.htmlMailing List, Third Party Advisory
Other references
- access.redhat.com/errata/RHSA-2026:26562
- access.redhat.com/errata/RHSA-2026:26566
- access.redhat.com/errata/RHSA-2026:26590
- access.redhat.com/errata/RHSA-2026:26610
- access.redhat.com/errata/RHSA-2026:26709
- access.redhat.com/errata/RHSA-2026:28923
- access.redhat.com/errata/RHSA-2026:29844
- access.redhat.com/errata/RHSA-2026:36083
- access.redhat.com/errata/RHSA-2026:36085
- access.redhat.com/errata/RHSA-2026:36086
- access.redhat.com/errata/RHSA-2026:36087
- access.redhat.com/errata/RHSA-2026:36632
- access.redhat.com/errata/RHSA-2026:36633
- access.redhat.com/errata/RHSA-2026:36634
- access.redhat.com/errata/RHSA-2026:36768
Other vulnerabilities in Red Hat Enterprise Linux 10
- 8.8 High severity
- 7.5 High severity
- 7.5 High severity
- 7.9 High severity
- 7.3 High severity
- 7.5 High severity
Recent Stack-based Buffer Overflow vulnerabilities
- 7.8 High severity
- 7.8 High severity
- 8.8 High severity
- 8.3 High severity
- 7.5 High severity
- 7.8 High severity
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