CVE-2026-55999

HIGHNVD 7.88.5▲
EchelonGraph scoreHIGH confidence

Score 8.5 from GitHub Security Advisory (severity: HIGH) published 2026-07-08. NVD baseline CVSS 7.8; sources differ by 0.7.

Triggered by: GitHub Security Advisory CVSS
Sources: epss, ghsa, nvd
Trending — Patch released this week
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.

Local attackers with a X connection able to provide PCX fonts to the X server xorg-server before 21.2.24 and xwayland before 24.1.13 could cause a heap buffer overflow via SetFont due to missing glyph boundary checks.

CVSS v3
7.8
EG Score
8.5(high)
EPSS
11.5%
KEV
Not listed

Published

July 8, 2026

Last Modified

July 9, 2026

Advisory Details (2)

Auto-updated Jul 8, 2026
No patch confirmed yet.
generic

oss-security - FW: X.Org Security Advisory: multiple security issues X.Org X server and Xwayland

https://www.openwall.com/lists/oss-security/2026/07/08/2
generic

glamor: reject fonts with per-glyph metrics exceeding maxbounds (fbf7bac2) · Commits · xorg / xserver · GitLab

https://gitlab.freedesktop.org/xorg/xserver/-/commit/fbf7bac22e2c6bd627fb042742a23318263edae1

Vendor Advisories for CVE-2026-55999(5)

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

Patch Availability(5)

Vendor / EcosystemFixed in / PatchReleasedSource
redhatxorg-x11-server-Xwayland-0:24.1.9-4.el10_2.32026-07-13redhat
redhatxorg-x11-server-0:1.20.11-28.el8_10.32026-07-13redhat
redhatxorg-x11-server-Xwayland-0:21.1.3-20.el8_10.32026-07-13redhat
redhatxorg-x11-server-0:1.20.11-34.el9_8.32026-07-13redhat
redhatxorg-x11-server-Xwayland-0:24.1.9-4.el9_8.32026-07-13redhat

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

(2)

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 38× in last 7d / 38× 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.

  1. 2026-07-13 22:31 UTCEPSS rescore
  2. 2026-07-13 19:49 UTCEG score recompute
  3. 2026-07-13 19:49 UTCVendor advisory
  4. 2026-07-13 19:49 UTCGHSA enrichment
  5. 2026-07-13 08:52 UTCEG score recompute
  6. 2026-07-13 08:52 UTCGHSA enrichment
  7. 2026-07-13 06:13 UTCEPSS rescore
  8. 2026-07-13 06:13 UTCEPSS rescore
  9. 2026-07-12 21:55 UTCEG score recompute
  10. 2026-07-12 21:55 UTCGHSA enrichment
  11. 2026-07-12 10:58 UTCEG score recompute
  12. 2026-07-12 10:58 UTCGHSA enrichment
  13. 2026-07-12 05:46 UTCEPSS rescore
  14. 2026-07-12 00:01 UTCEG score recompute
  15. 2026-07-12 00:00 UTCGHSA enrichment
  16. 2026-07-11 13:03 UTCEG score recompute
  17. 2026-07-11 13:03 UTCGHSA enrichment
  18. 2026-07-11 08:27 UTCEPSS rescore
  19. 2026-07-11 08:27 UTCEPSS rescore
  20. 2026-07-11 02:05 UTCEG score recompute
  21. 2026-07-11 02:05 UTCGHSA enrichment
  22. 2026-07-10 15:07 UTCEG score recompute
  23. 2026-07-10 15:07 UTCGHSA enrichment
  24. 2026-07-10 04:06 UTCEG score recompute
  25. 2026-07-10 04:06 UTCGHSA enrichment
Show 13 more
  1. 2026-07-09 21:46 UTCNVD updateCVSS v3 → 7.8
  2. 2026-07-09 19:10 UTCEPSS rescore
  3. 2026-07-09 19:10 UTCEPSS rescore
  4. 2026-07-09 17:09 UTCEG score recompute
  5. 2026-07-09 17:09 UTCGHSA enrichment
  6. 2026-07-09 06:12 UTCEG score recompute
  7. 2026-07-09 06:11 UTCGHSA enrichment
  8. 2026-07-08 19:14 UTCEG score recompute
  9. 2026-07-08 19:14 UTCGHSA enrichment
  10. 2026-07-08 15:16 UTCEPSS rescore
  11. 2026-07-08 15:16 UTCEPSS rescore
  12. 2026-07-08 08:17 UTCEG score recompute
  13. 2026-07-08 08:16 UTCMITRE cvelistV5first tracked

Related CVEs(same vendor + same CWE)

Frequently asked(5)

What is CVE-2026-55999?
CVE-2026-55999 is a high vulnerability published on July 8, 2026. Local attackers with a X connection able to provide PCX fonts to the X server xorg-server before 21.2.24 and xwayland before 24.1.13 could cause a heap buffer overflow via SetFont due to missing glyph boundary checks.
When was CVE-2026-55999 disclosed?
CVE-2026-55999 was first published in the National Vulnerability Database on July 8, 2026, with the most recent update on July 9, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-55999 actively exploited?
CVE-2026-55999 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 11.5% percentile likelihood of exploitation in the next 30 days — higher percentiles indicate greater predicted risk.
What is the CVSS score of CVE-2026-55999?
CVE-2026-55999 has a CVSS v3 base score of 7.8 (NVD). EchelonGraph synthesises NVD + CISA KEV + FIRST EPSS + GHSA into a combined EG score of 8.5.
How do I remediate CVE-2026-55999?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-55999, 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-2026-55999

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