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)
EG Risk
—
EPSS
30.6%
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
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 / 37× 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 128 total refreshes for this CVE.

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

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 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 30.6% 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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