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: 0.2%CVSS: 7.8Exploit: None knownExposed services: Not assessed

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
7.8HIGHmedium confidence
EG Risk
35
EG Risk 35/100

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%
EPSS PROB
0.2%
EPSS %ILE
7th
KEV
Not listed

Published

April 23, 2026

Last Modified

July 15, 2026

Advisory Details (7)

Auto-updated Apr 29, 2026
Patch available. Sources: redhat.
redhatMentions a patch (unverified)

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
redhatMentions a patch (unverified)

cve-details

https://access.redhat.com/security/cve/CVE-2026-33999
redhatMentions a patch (unverified)

Affected: Red Hat Enterprise Linux 8.

https://access.redhat.com/errata/RHSA-2026:11692
redhatMentions a patch (unverified)

Affected: Red Hat Enterprise Linux 9.

https://access.redhat.com/errata/RHSA-2026:11388
redhatMentions a patch (unverified)

Affected: Red Hat Enterprise Linux 9.

https://access.redhat.com/errata/RHSA-2026:11369
redhatMentions a patch (unverified)

Affected: Red Hat Enterprise Linux 10.

https://access.redhat.com/errata/RHSA-2026:11352
redhatMentions a patch (unverified)

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 / EcosystemFix (by version range) / 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 rangeFix by version rangeDependents
xorg-server2:21.1.7-3 ... 2:21.1.7-3+deb12u9 (12 versions)
  • every version up to 2:21.1.7-3+deb12u12: fixed in 2:21.1.7-3+deb12u12
—
xwayland2:22.1.9-1 ... 2:24.1.9-1 (24 versions)
  • every version on: no fix on record
—
Debian:13(2)
PackageVulnerable rangeFix by version rangeDependents
xorg-server2:21.1.16-1.3, 2:21.1.16-1.3+deb13u1
  • every version up to 2:21.1.16-1.3+deb13u2: fixed in 2:21.1.16-1.3+deb13u2
—
xwayland2:24.1.10-1 ... 2:24.1.9-1 (7 versions)
  • every version on: no fix on record
—
Debian:14(2)
PackageVulnerable rangeFix by version rangeDependents
xorg-server2:21.1.16-1.3, 2:21.1.18-1, 2:21.1.18-2, 2:21.1.20-1, 2:21.1.21-1
  • every version up to 2:21.1.22-1: fixed in 2:21.1.22-1
—
xwayland2:24.1.6-1, 2:24.1.8-1, 2:24.1.9-1
  • every version up to 2:24.1.10-1: fixed in 2:24.1.10-1
—
Debian:11(1)
PackageVulnerable rangeFix by version rangeDependents
xorg-server2:1.20.11-1 ... 2:21.1.9-1+hurd.1 (61 versions)
  • every version on: no fix on record
—

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 / 25× 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 250 total refreshes for this CVE.

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

Related CVEs(same product + same vendor + same CWE)

Same vendor

5 shown

redhat:RHSA-2026:10739 · redhat:RHSA-2026:19342 · redhat:RHSA-2026:20547

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 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 0.2% probability of exploitation in the next 30 days (7th percentile of EPSS-scored CVEs).
What is the CVSS score of CVE-2026-33999?
CVE-2026-33999 has a CVSS base score of 7.8 (a secondary CVSS source that NVD displays; NVD's own analysis pending).
How do I remediate CVE-2026-33999?
A fix for CVE-2026-33999 is available: update to the fixed version the vendor names in its advisory. The vendor advisories EchelonGraph has for CVE-2026-33999 are linked in the Vendor Advisories panel on this page.

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.

Book a Demo →Browse All CVEs