CVE-2026-33999

Description

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.

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CVSS v3.1 Score

7.8

HIGH

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

EPSS — Exploit Prediction

0.0001

Probability of exploitation

0.00%

Percentile rank

EPSS estimates the probability that this vulnerability will be exploited in the wild within the next 30 days. A higher score means more likely to be exploited.

Weakness Type (CWE)

CWE-191 CWE-191

References

Other References

https://access.redhat.com/errata/RHSA-2026:10739 https://access.redhat.com/errata/RHSA-2026:11352 https://access.redhat.com/errata/RHSA-2026:11369 https://access.redhat.com/errata/RHSA-2026:11388 https://access.redhat.com/errata/RHSA-2026:11656 https://access.redhat.com/errata/RHSA-2026:11692 https://access.redhat.com/errata/RHSA-2026:13414 https://access.redhat.com/security/cve/CVE-2026-33999 https://bugzilla.redhat.com/show_bug.cgi?id=2451106

Frequently Asked Questions

What is CVE-2026-33999? +

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. It has a CVSS v3.1 base score of 7.8 (HIGH).

How severe is CVE-2026-33999? +

CVE-2026-33999 has a CVSS v3.1 score of 7.8 out of 10, rated HIGH. This is a high-severity vulnerability that should be prioritized for patching. The EPSS score is 0.0001, placing it in the 0th percentile for exploitation probability.

How do I check if I'm vulnerable to CVE-2026-33999? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

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