CVE-2026-33999High· 7.8▾ TwilightA flaw was found in the X.Org X server. This integer underflow vulnerability, specifically in the XKB compatibility map handling, allows an attacker with local or remote X11 server access to trigger a buffer read overrun. This can lead t…
▾ Twilight zone — High severity, or a signal on a lesser flaw
impact 42.9 · likelihood 0.1 · exploitation 0
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Stakeholder-Specific Vulnerability Categorization from CISA's ADP record at CVE.org: whether exploitation is observed, whether an attack can be automated, and how much of the system is at stake. The CVSS score shown above comes from the assigning CNA record, not NVD.
Disclosure to exploitation, from the record and what we observed since indexing it.
Disclosed via CVEORG
Last analysed / modified upstream
0.4%
A flaw was found in the X.Org X server. This integer underflow vulnerability, specifically in the XKB compatibility map handling, allows an attacker with local or remote X11 server access to trigger a buffer read overrun. This can lead to memory-safety violations and potentially a denial of service (DoS) or other severe impacts.
xorg-x11-server-Xwayland (all versions)xorg-x11-server-Xwayland (all versions)xorg-x11-server-Xwayland (all versions)tigervnc (all versions)xorg-x11-server (all versions)tigervnc (all versions)xorg-x11-server-Xwayland (all versions)xorg-x11-server (all versions)tigervnc (all versions)xorg-x11-server (all versions)tigervnc (all versions)xorg-x11-server (all versions)tigervnc (all versions)xorg-x11-server-Xwayland (all versions)xorg-x11-server (all versions)tigervnc (all versions)tigervnc (all versions)xorg-x11-server-Xwayland (all versions)xorg-x11-server (all versions)xorg-x11-server-Xwayland (all versions)xorg-x11-server (all versions)xorg-x11-server-Xwayland (all versions)xorg-x11-server (all versions)tigervnc (all versions)xorg-x11-server-Xwayland (all versions)xorg-x11-server (all versions)tigervnc (all versions)tigervnc (all versions)xorg-x11-server-Xwayland (all versions)xorg-x11-server (all versions)tigervnc (all versions)xorg-x11-server (all versions)xorg-x11-server-Xwayland (all versions)xorg-x11-server-Xwayland (all versions)xorg-x11-server (all versions)tigervnc (all versions)xorg-x11-server-Xwayland (all versions)xorg-x11-server (all versions)tigervnc (all versions)xorg-x11-server (all versions)xorg-x11-server-Xwayland (all versions)tigervnc (all versions)xorg-x11-server (all versions)xorg-x11-server-Xwayland (all versions)tigervnc (all versions)xorg-x11-serverRefer to the linked advisories for vendor-supplied fixes and affected version ranges.
To mitigate this issue, restrict access to the X11 server. For remote access, disable X11 forwarding in SSH configurations if not required. Edit /etc/ssh/sshd_config and set X11Forwarding no. After modifying the configuration, restart the sshd service using systemctl restart sshd. Disabling X11 forwarding may impact remote graphical applications.
Connected by shared product, vendor, weakness, or advisory.
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