Red Hat Enterprise Linux 10.0 Extended Update…: Buffer Access with Incorrect Length Value
CVE-2026-34002 is a critical-severity buffer access with incorrect length value vulnerability in Red Hat Enterprise Linux 10.0 Extended Update Support from Red Hat, with a CVSS 3.1 base score of 9.1 out of 10. It can be exploited remotely over the network by an unauthenticated attacker, without any action from a user. There is no confirmed exploitation so far. EPSS estimates a 0.49% chance of exploitation within 30 days, which is low compared with other CVEs.
Critical severity: a successful attack would have severe impact.
What to do
- Check which version of Red Hat Enterprise Linux 10.0 Extended Update Support you run against the affected versions below, and install the vendor's latest release.
- Until you can update, restrict network access to the affected service so it is not reachable from untrusted networks.
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
- NetworkCan be exploited remotely over a network, including the internet.
- Attack complexity
- LowNo special conditions are needed; the attack works reliably.
- Privileges required
- NoneNo account or login is needed.
- 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
- NoneNothing can be modified.
- Availability
- HighThe component can be taken down completely.
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:H. Scored by NVD.
| Scoring system | Score | Severity | Scored by |
|---|---|---|---|
| CVSS 3.1 | 6.1 | Medium | CNA (redhat.com) |
| CVSS 3.1 | 9.1 | Critical | NVD |
Official description
A flaw was found in the X.Org X server. This vulnerability, an out-of-bounds read, affects the XKB (X Keyboard Extension) modifier map handling. An attacker with access to the X11 server can exploit this by sending a malformed request, which causes the server to read beyond its intended memory boundaries. This can lead to the exposure of sensitive information or cause the server to crash, resulting in a denial of service.
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
The underlying weakness: Buffer Access with Incorrect Length Value
The product uses a sequential operation to read or write a buffer, but it uses an incorrect length value that causes it to access memory that is outside of the bounds of the buffer.
How developers prevent this class of flaw
- Use a language that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid. For example, many languages that perform their own memory management, such as Java and Perl, are not subject to buffer overflows. Other languages, such as Ada and C#, typically provide overflow protection, but the protection can be disabled by the programmer. Be wary that a language's interface to native code may still be subject to overflows, even if the language itself is theoretically safe.
- Use a vetted library or framework that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid. Examples include the Safe C String Library (SafeStr) by Messier and Viega, and the Strsafe.h library from Microsoft. These libraries provide safer versions of overflow-prone string-handling functions.
- 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.
More Buffer Access with Incorrect Length Value vulnerabilities (CWE-805)
Timeline
- CVE record published.
- CISA published its SSVC assessment (exploitation: none, automatable: no, technical impact: partial).
- Record last changed materially (score, affected products, status or references).
References
Third-party and government advisories
- access.redhat.com/security/cve/CVE-2026-34002Third Party Advisory
- bugzilla.redhat.com/show_bug.cgi?id=2451112Issue Tracking, Third Party Advisory
Other references
- access.redhat.com/errata/RHSA-2026:20547
- access.redhat.com/errata/RHSA-2026:20555
- access.redhat.com/errata/RHSA-2026:20557
- access.redhat.com/errata/RHSA-2026:20558
- access.redhat.com/errata/RHSA-2026:20560
- access.redhat.com/errata/RHSA-2026:20561
- access.redhat.com/errata/RHSA-2026:20562
- access.redhat.com/errata/RHSA-2026:20563
- access.redhat.com/errata/RHSA-2026:20575
- access.redhat.com/errata/RHSA-2026:20576
- access.redhat.com/errata/RHSA-2026:20590
- access.redhat.com/errata/RHSA-2026:21699
- access.redhat.com/errata/RHSA-2026:21712
- access.redhat.com/errata/RHSA-2026:21715
- access.redhat.com/errata/RHSA-2026:21716
Other vulnerabilities in Red Hat Enterprise Linux 10.0 Extended Update Support
- 9.8 Critical severity
- 8.6 High severity
- 8.6 High severity
- 8.2 High severity
- 8.6 High severity
- 8.6 High severity
Recent Buffer Access with Incorrect Length Value vulnerabilities
- 7.4 High severity
- 7.4 High severity
- 7.3 High severity
- 7.3 High severity
- 7.3 High severity
- 7.3 High severity
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