CVE-2026-33999: xorg-server Integer Underflow (Wrap or Wraparound)
Vulnerability summary
CVE-2026-33999 is a high (CVSS 7.8) Integer Underflow (Wrap or Wraparound) vulnerability in xorg-server. EPSS estimates a 0.19% chance of exploitation in the next 30 days, higher than 7.7% of scored vulnerabilities.
Advisory lineage
Upstream 0 · Downstream 48 · Related 12Timeline
- 23-04-2026PublishedVulnerability first disclosed.
- 15-07-2026Last modifiedVulnerability information updated.
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.
CVSS metrics
4 scores · 4 sources · 1 version- OSV · UbuntuEcosystem advisory · calculated7.8HighCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
- OSV · DebianEcosystem advisory · calculated7.8HighCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
- NVDNIST7.8HighCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
EPSS trend
Probability
0.19%
Chance of exploitation in the next 30 days
Percentile
8%
Versus all other CVEs
30-day change
-0.19 pp
From 0.38% on 19-09-2026
Known exploited
Compare KEV catalogsNot in any of the 3 tracked catalogs.
Public exploits
0 foundNo public exploits indexed.
Weaknesses
CWE · root causeAffected systems
Ubuntu4 products
- xorg-serverAll versions (No fix recorded)
- xorg-server-hwe-16.04All versions (No fix recorded)
- xorg-server-hwe-18.04All versions (No fix recorded)
- xwaylandAll versions (No fix recorded)
Debian2 products
- xorg-server< 2:21.1.7-3+deb12u12 | < 2:21.1.16-1.3+deb13u2 | < 2:21.1.22-1
- xwaylandAll versions (No fix recorded) | < 2:24.1.10-1
2 vendors · 6 products
