#VU104192 Heap-based buffer overflow in X.org Server and Xwayland - CVE-2025-26596

Vulnerability identifier: #VU104192

Vulnerability risk: Low

CVSSv4.0: 5.9 [CVSS:4.0/AV:L/AC:L/AT:N/PR:L/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:U/U:Clear]

CVE-ID: CVE-2025-26596

CWE-ID: CWE-122

Exploitation vector: Local

Exploit availability: No

Vulnerable software:
X.org Server
Server applications / Other server solutions
Xwayland
Client/Desktop applications / Multimedia software

Vendor: X.org

Description

The vulnerability allows a local user to escalate privileges on the system.

The vulnerability exists due to a boundary error within the XkbWriteKeySyms() function. A local user can  trigger a heap-based buffer overflow and execute arbitrary code with elevated privileges.

Mitigation
Install updates from vendor's website.

Vulnerable software versions

X.org Server: 21.0.99.1 - 21.1.15

Xwayland: 21.0.99.901 - 24.1.5

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External links
https://bugzilla.redhat.com/show_bug.cgi?id=2345256
https://gitlab.freedesktop.org/xorg/xserver/-/commit/80d69f01
https://www.zerodayinitiative.com/advisories/ZDI-25-141/

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Q & A

Can this vulnerability be exploited remotely?

No. This vulnerability can be exploited locally. The attacker should have authentication credentials and successfully authenticate on the system.

Is there known malware, which exploits this vulnerability?

No. We are not aware of malware exploiting this vulnerability.