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
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 13× in last 7d / 41× 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 138 total refreshes for this CVE.

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

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 0% probability of exploitation in the next 30 days, which ranks it in the top 69.4% 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

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

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