Vulnerability · CVE-2026-33999
A flaw was found in the X.Org X server.
Published Apr 23, 2026 · catalog updated Jul 15, 2026 · A flaw was found
Check if you run it
No confirmed exploitation is on record for CVE-2026-33999. EPSS is 0.19%. Act only if a listed version of A flaw was found is installed.
Gaps on this record
- The stored product name is a package slug. The name on this page is taken from the title (A flaw was found).
- No version range is stored. A customer cannot check an installed version against this record.
- No vendor fix or required action is stored. Compare the linked advisory before you change production.
- Severity
- High7.8
- Known exploitation
- Not in CISA/VulnCheck KEV
- EPSS
- 0.19%
- Remediation
- Not established
- Affected products
- See sources for product scope
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.
No affected version ranges are stored yet. Use the vendor advisory before you decide this record does not apply.
How to fix CVE-2026-33999
Recommended remediation
No required-action text, fix commit, or clear fixed-version range is stored yet.
Official advisories
What to do
Three questions, each answered from this record only. Confirm the vendor advisory before you patch.
Should you patch?
No confirmed exploitation is on record for CVE-2026-33999. EPSS is 0.19%. Act only if a listed version of A flaw was found is installed.
Which versions are affected?
Affected version ranges are not on this record. Compare the installed version with the linked vendor advisory before you change production.
What should an analyst verify?
CWE-191: Integer Underflow. EPSS 0.19%. There is no CISA KEV listing. No Exploit-DB or Metasploit reference is linked. Use the source links for the original advisory.
Code
The project this record applies to. Exploit listings stay in References.
No public source repository is identified for this product.
Timeline
Detection, updates, and resolution for this record.
Apr 23, 2026 · NIST NVD
Detected
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.
Jul 15, 2026 · NIST NVD
Updated
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.
Sources
- CVE.orgVulnerability recordCVE-2026-33999
Official CVE identifier
cve.org - FIRST EPSSExploitation probabilityCVE-2026-33999
30-day exploitation probability 0.2%
first.org - NIST NVDVulnerability recordCVE-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
nvd.nist.gov
References
Freshness
Last verified in this catalog Oct 18, 2026. Significant claims (KEV, EPSS, CVSS, affected ranges) come from the source rows above — open the original publisher for the authoritative advisory.