CVE-2026-33999

HIGHPre-NVD 7.87.8—
EchelonGraph scoreMEDIUM confidence

Score 7.8 from GitHub Security Advisory (severity: HIGH) published 2026-04-23. a secondary CVSS source baseline 7.8; sources differ by 0.0.

Triggered by: GitHub Security Advisory CVSS
Sources: epss, ghsa, secondary
7.8EG
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS PROB: 0%CVSS: 7.8Exploit: None knownExposed: 0

A fix is available — apply it.

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 v3
7.8
EG Score
7.8(medium)
EG Risk
35(Track)
EG Risk 35/100SSVC: Track

EG Risk is EchelonGraph's 0–100 priority score: it fuses intrinsic severity with real-world exploitation and automatability so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner. Distinct from the 0–10 EG Score (severity).

How it’s computed
Severity78% × 45%
Exploitation0% × 40%
Automatability0% × 15%
Action: Routine — remediate on your standard cadence.
EPSS PROB
0%
EPSS %ILE
31%
KEV
Not listed

Published

April 23, 2026

Last Modified

July 15, 2026

Advisory Details (7)

Auto-updated Apr 29, 2026
Patch available. Sources: redhat.
redhat Patch Available

2451106 – (CVE-2026-33999) CVE-2026-33999 xorg: xwayland: X.Org X server: Denial of Service via integer underflow in XKB compatibility map handling

Affected: Red Hat Enterprise Linux 9

https://bugzilla.redhat.com/show_bug.cgi?id=2451106
redhat Patch Available

cve-details

https://access.redhat.com/security/cve/CVE-2026-33999
redhat Patch Available

Affected: Red Hat Enterprise Linux 8.

https://access.redhat.com/errata/RHSA-2026:11692
redhat Patch Available

Affected: Red Hat Enterprise Linux 9.

https://access.redhat.com/errata/RHSA-2026:11388
redhat Patch Available

Affected: Red Hat Enterprise Linux 9.

https://access.redhat.com/errata/RHSA-2026:11369
redhat Patch Available

Affected: Red Hat Enterprise Linux 10.

https://access.redhat.com/errata/RHSA-2026:11352
redhat Patch Available

Affected: Red Hat Enterprise Linux 9.

https://access.redhat.com/errata/RHSA-2026:10739

Vendor Advisories for CVE-2026-33999(20)

These vendors published their own advisory mentioning this CVE — often with vendor-specific remediation steps + affected product lists not in NVD.

Patch Availability(30)

Vendor / EcosystemFixed in / PatchReleasedSource
redhattigervnc-0:1.12.0-6.el8_6.172026-06-08redhat
redhattigervnc-0:1.12.0-15.el8_8.172026-06-04redhat
redhattigervnc-0:1.1.0-25.el6_10.162026-06-04redhat
redhattigervnc-0:1.11.0-8.el8_4.152026-06-04redhat
redhattigervnc-0:1.8.0-36.el7_9.42026-06-02redhat
redhattigervnc-0:1.14.1-10.el9_62026-06-02redhat
redhatxorg-x11-server-0:1.20.10-4.el8_42026-05-28redhat
redhatxorg-x11-server-Xwayland-0:21.1.3-2.el8_6.62026-05-28redhat
redhatxorg-x11-server-0:1.20.11-13.el9_02026-05-28redhat
redhatxorg-x11-server-0:1.20.11-18.el8_82026-05-28redhat
redhatxorg-x11-server-Xwayland-0:21.1.3-13.el8_82026-05-28redhat
redhattigervnc-0:1.11.0-22.el9_0.172026-05-28redhat
redhatxorg-x11-server-0:1.20.11-7.el8_62026-05-28redhat
redhatxorg-x11-server-Xwayland-0:21.1.3-5.el9_02026-05-26redhat
redhatxorg-x11-server-0:1.20.11-33.el9_62026-05-26redhat
redhatxorg-x11-server-0:1.20.11-20.el9_22026-05-26redhat
redhatxorg-x11-server-Xwayland-0:22.1.9-8.el9_42026-05-26redhat
redhatxorg-x11-server-Xwayland-0:24.1.5-6.el10_02026-05-26redhat
redhatxorg-x11-server-Xwayland-0:23.2.7-6.el9_62026-05-26redhat
redhatxorg-x11-server-0:1.20.4-34.el7_92026-05-26redhat
redhattigervnc-0:1.13.1-8.el9_4.92026-05-26redhat
redhatxorg-x11-server-Xwayland-0:21.1.3-10.el9_22026-05-26redhat
redhatxorg-x11-server-0:1.20.11-28.el9_42026-05-26redhat
redhattigervnc-0:1.12.0-14.el9_2.142026-05-26redhat
redhatxorg-x11-server-0:1.20.11-34.el9_82026-05-19redhat
redhattigervnc-0:1.15.0-7.el9_8.12026-05-19redhat
redhatxorg-x11-server-Xwayland-0:24.1.9-4.el9_82026-05-19redhat
redhatxorg-x11-server-Xwayland-0:24.1.9-4.el10_22026-05-19redhat
redhattigervnc-0:1.15.0-9.el8_102026-05-04redhat
redhatxorg-x11-server-0:1.20.11-28.el8_102026-04-29redhat

Patches are aggregated from vendor advisories (Red Hat, Microsoft, Cisco, GitHub) and package ecosystems (OSV, GHSA). Multiple rows for the same upstream release have been deduplicated.

Affected Packages

(7 across 4 ecosystems)
Debian:12(2)
PackageVulnerable rangeFixed inDependents
xorg-server2:21.1.7-3 ... 2:21.1.7-3+deb12u9 (12 versions)2:21.1.7-3+deb12u12—
xwayland2:22.1.9-1 ... 2:24.1.9-1 (23 versions)——
Debian:13(2)
PackageVulnerable rangeFixed inDependents
xorg-server2:21.1.16-1.3, 2:21.1.16-1.3+deb13u12:21.1.16-1.3+deb13u2—
xwayland2:24.1.10-1 ... 2:24.1.9-1 (6 versions)——
Debian:14(2)
PackageVulnerable rangeFixed inDependents
xorg-server2:21.1.16-1.3, 2:21.1.18-1, 2:21.1.18-2, 2:21.1.20-1, 2:21.1.21-12:21.1.22-1—
xwayland2:24.1.6-1, 2:24.1.8-1, 2:24.1.9-12:24.1.10-1—
Debian:11(1)
PackageVulnerable rangeFixed inDependents
xorg-server2:1.20.11-1 ... 2:21.1.9-1+hurd.1 (61 versions)——

Weakness Classification(1)

MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.

Additional Vendor Advisories

(16)

Vendors that published advisories for this CVE beyond the curated set above. Broader coverage but minimal per-row detail — click through for the original advisory.

Data Freshness Timeline

(refreshed 7× in last 7d / 76× in last 30d)

Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. Most recent first.

Showing the most recent 100 of 213 total refreshes for this CVE.

  1. 2026-08-25 13:49 UTCEPSS rescore
  2. 2026-08-24 14:17 UTCEPSS rescore
  3. 2026-08-23 00:19 UTCEPSS rescore
  4. 2026-08-21 23:49 UTCEPSS rescore
  5. 2026-08-20 22:55 UTCEPSS rescore
  6. 2026-08-20 22:55 UTCEPSS rescore
  7. 2026-08-19 17:03 UTCEPSS rescore
  8. 2026-08-18 13:48 UTCEPSS rescore
  9. 2026-08-17 14:59 UTCEG score recompute
  10. 2026-08-17 14:59 UTCVendor advisory
  11. 2026-08-17 14:59 UTCGHSA enrichment
  12. 2026-08-17 13:47 UTCEPSS rescore
  13. 2026-08-16 14:56 UTCEPSS rescore
  14. 2026-08-16 05:54 UTCEG score recompute
  15. 2026-08-16 05:54 UTCVendor advisory
  16. 2026-08-16 05:54 UTCGHSA enrichment
  17. 2026-08-16 02:14 UTCEPSS rescore
  18. 2026-08-15 01:30 UTCEPSS rescore
  19. 2026-08-14 17:04 UTCVendor advisory
  20. 2026-08-14 17:04 UTCGHSA enrichment
  21. 2026-08-14 04:14 UTCEG score recompute
  22. 2026-08-14 04:14 UTCVendor advisory
  23. 2026-08-14 04:14 UTCGHSA enrichment
  24. 2026-08-13 22:00 UTCEPSS rescore
  25. 2026-08-13 08:37 UTCVendor advisory
Show 75 more
  1. 2026-08-13 08:37 UTCGHSA enrichment
  2. 2026-08-12 17:59 UTCEG score recompute
  3. 2026-08-12 17:59 UTCVendor advisory
  4. 2026-08-12 17:59 UTCGHSA enrichment
  5. 2026-08-12 13:50 UTCEPSS rescore
  6. 2026-08-11 16:43 UTCEG score recompute
  7. 2026-08-11 16:43 UTCVendor advisory
  8. 2026-08-11 16:43 UTCGHSA enrichment
  9. 2026-08-11 02:14 UTCEG score recompute
  10. 2026-08-11 02:14 UTCVendor advisory
  11. 2026-08-11 02:14 UTCGHSA enrichment
  12. 2026-08-11 00:00 UTCEPSS rescore
  13. 2026-08-10 04:19 UTCVendor advisory
  14. 2026-08-10 04:19 UTCGHSA enrichment
  15. 2026-08-09 15:52 UTCEG score recompute
  16. 2026-08-09 15:52 UTCVendor advisory
  17. 2026-08-09 15:52 UTCGHSA enrichment
  18. 2026-08-09 13:46 UTCEPSS rescore
  19. 2026-08-09 03:26 UTCEG score recompute
  20. 2026-08-09 03:26 UTCVendor advisory
  21. 2026-08-09 03:26 UTCGHSA enrichment
  22. 2026-08-08 16:37 UTCEPSS rescore
  23. 2026-08-08 01:08 UTCEG score recompute
  24. 2026-08-08 01:08 UTCVendor advisory
  25. 2026-08-08 01:08 UTCGHSA enrichment
  26. 2026-08-07 12:41 UTCEG score recompute
  27. 2026-08-07 12:41 UTCVendor advisory
  28. 2026-08-07 12:41 UTCGHSA enrichment
  29. 2026-08-06 13:46 UTCEPSS rescore
  30. 2026-08-06 11:27 UTCVendor advisory
  31. 2026-08-06 11:27 UTCGHSA enrichment
  32. 2026-08-05 23:00 UTCEG score recompute
  33. 2026-08-05 23:00 UTCVendor advisory
  34. 2026-08-05 23:00 UTCGHSA enrichment
  35. 2026-08-05 19:17 UTCEPSS rescore
  36. 2026-08-04 15:10 UTCEPSS rescore
  37. 2026-08-04 10:38 UTCEPSS rescore
  38. 2026-08-03 21:10 UTCEG score recompute
  39. 2026-08-03 21:10 UTCVendor advisory
  40. 2026-08-03 21:10 UTCGHSA enrichment
  41. 2026-08-03 10:36 UTCEPSS rescore
  42. 2026-08-03 00:41 UTCVendor advisory
  43. 2026-08-03 00:41 UTCGHSA enrichment
  44. 2026-08-02 11:55 UTCEG score recompute
  45. 2026-08-02 11:55 UTCVendor advisory
  46. 2026-08-02 11:55 UTCGHSA enrichment
  47. 2026-08-02 02:27 UTCEPSS rescore
  48. 2026-08-01 04:16 UTCEPSS rescore
  49. 2026-07-30 16:28 UTCEPSS rescore
  50. 2026-07-30 01:30 UTCEPSS rescore
  51. 2026-07-27 14:13 UTCEPSS rescore
  52. 2026-07-26 14:54 UTCEPSS rescore
  53. 2026-07-26 14:54 UTCEPSS rescore
  54. 2026-07-25 14:18 UTCEPSS rescore
  55. 2026-07-25 14:18 UTCEPSS rescore
  56. 2026-07-24 14:17 UTCEPSS rescore
  57. 2026-07-24 14:17 UTCEPSS rescore
  58. 2026-07-23 14:18 UTCEPSS rescore
  59. 2026-07-23 14:18 UTCEPSS rescore
  60. 2026-07-23 03:09 UTCEG score recompute
  61. 2026-07-22 14:08 UTCEPSS rescore
  62. 2026-07-21 15:24 UTCEPSS rescore
  63. 2026-07-20 17:08 UTCEPSS rescore
  64. 2026-07-19 14:31 UTCEPSS rescore
  65. 2026-07-19 02:29 UTCEPSS rescore
  66. 2026-07-18 10:04 UTCEPSS rescore
  67. 2026-07-16 17:03 UTCEPSS rescore
  68. 2026-07-15 16:57 UTCEPSS rescore
  69. 2026-07-15 16:57 UTCEPSS rescore
  70. 2026-07-15 02:00 UTCEPSS rescore
  71. 2026-07-13 22:30 UTCEPSS rescore
  72. 2026-07-13 06:13 UTCEPSS rescore
  73. 2026-07-13 06:13 UTCEPSS rescore
  74. 2026-07-12 05:46 UTCEPSS rescore
  75. 2026-07-11 08:27 UTCEPSS rescore

Frequently asked(5)

What is CVE-2026-33999?
CVE-2026-33999 is a high vulnerability published on April 23, 2026. 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…
When was CVE-2026-33999 disclosed?
CVE-2026-33999 was first published in the National Vulnerability Database on April 23, 2026, with the most recent update on July 15, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-33999 actively exploited?
CVE-2026-33999 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0% probability of exploitation in the next 30 days, which ranks it in the top 69.2% of all scored CVEs.
What is the CVSS score of CVE-2026-33999?
CVE-2026-33999 has a CVSS v3 base score of 7.8 (NVD).
How do I remediate CVE-2026-33999?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-33999, EchelonGraph cross-links them in the Vendor Advisories panel below — those typically contain the canonical remediation steps, fixed version numbers, and any vendor-specific mitigations.

Dependency Blast Radius

See which npm, PyPI, Go, and Maven packages are affected by CVE-2026-33999

Explore →

Is Your Infrastructure Affected by CVE-2026-33999?

EchelonGraph automatically scans your cloud infrastructure and maps CVE exposure using blast radius analysis.

Start Free Scan →Browse All CVEs