PatchSiren cyber security CVE debrief

CVE-2026-34003 Red Hat CVE debrief

A local out-of-bounds memory access vulnerability exists in the X.Org X server's XKB key types request validation. An attacker with local access can send a crafted request to trigger the flaw, potentially causing information disclosure, server crash (DoS), or higher impact outcomes in certain configurations. The vulnerability was published on 2026-04-23 and last modified on 2026-05-20. Multiple Red Hat security advisories have been issued addressing this issue. The weakness is classified as CWE-125 (Out-of-bounds Read).

Vendor: Red Hat
Product: Red Hat Enterprise Linux 10
CVSS: HIGH 7.8
CISA KEV: Not listed in stored evidence
Original CVE published: 2026-04-23
Original CVE updated: 2026-05-20
Advisory published: 2026-04-23
Advisory updated: 2026-05-20

Who should care

Organizations running X.Org X server on Linux systems, particularly those with multi-user environments where untrusted users have local access. System administrators managing Red Hat Enterprise Linux deployments should prioritize patching based on the available RHSA advisories.

Technical summary

The vulnerability exists in the XKB (X Keyboard Extension) key types request validation within the X.Org X server. Insufficient bounds checking on key types requests allows a local attacker to trigger out-of-bounds memory access. The attack vector is local (AV:L) with low attack complexity (AC:L) and low privileges required (PR:L). Successful exploitation can result in high impact to confidentiality, integrity, and availability (C:H/I:H/A:H). The flaw is classified as CWE-125 (Out-of-bounds Read).

Defensive priority

high

Recommended defensive actions

Apply vendor patches from Red Hat security advisories for affected systems
Restrict local access to X server where patching is not immediately feasible
Monitor for anomalous X server crashes or unexpected memory access patterns
Review X server configuration for exposure to untrusted local users
Validate XKB extension usage and consider disabling if not required

Evidence notes

Vulnerability description sourced from official CVE record and NVD entry. Red Hat has issued multiple RHSA advisories (RHSA-2026:10739, RHSA-2026:11352, RHSA-2026:11369, RHSA-2026:11388, RHSA-2026:11656, RHSA-2026:11692, RHSA-2026:13414, RHSA-2026:19125, RHSA-2026:19342, RHSA-2026:19343, RHSA-2026:19344) indicating patches are available for affected Red Hat Enterprise Linux systems. Bugzilla reference 2451113 tracks this issue. CVSS 3.1 vector: AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H.

Official resources

2026-04-23