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
7.8
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS: 0%CVSS: 7.8Exploit: NoneExposed: 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)
EPSS
30.0%
KEV
Not listed

Published

April 23, 2026

Last Modified

June 30, 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
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-0:1.20.11-34.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-Xwayland-0:21.1.3-20.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.

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 / 73× 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 131 total refreshes for this CVE.

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

Related CVEs(same vendor + same CWE)

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 June 30, 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 30.0% percentile likelihood of exploitation in the next 30 days — higher percentiles indicate greater predicted risk.
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

Explore the affected products and dependency analysis for CVE-2026-33999

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