CVE-2025-26595: Xorg: xwayland: buffer overflow in xkbvmodmasktext()

Severity: high (CVSS 7.8 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.4% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2025-02-25 · updated 2026-06-29
Weakness: CWE-121

Description

A buffer overflow flaw was found in X.Org and Xwayland. The code in XkbVModMaskText() allocates a fixed-sized buffer on the stack and copies the names of the virtual modifiers to that buffer. The code fails to check the bounds of the buffer and would copy the data regardless of the size.

Affected products

Red Hat Enterprise Linux: 7.0, 8.0, 9.0
Kaspersky TigerVNC: all versions
xorg-x11-server: before 21.1.16 — fixed in 21.1.16
X.Org xwayland: before 24.1.6 — fixed in 24.1.6

How to fix

Upgrade to a fixed version: xorg-x11-server 21.1.16; X.Org xwayland 24.1.6. Check the vendor advisory for mitigations.

References

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