CVE-2026-8955

HIGHNVD 8.86.5▼
EchelonGraph scoreMEDIUM confidence

Score 6.5 from GitHub Security Advisory published 2026-05-19. NVD baseline CVSS 8.8; sources differ by 2.3.

Triggered by: GitHub Security Advisory CVSS
Sources: epss, ghsa, nvd
8.8
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS: 0%CVSS: 8.8Exploit: NoneExposed: 0

A fix is available — apply it.

Privilege escalation in the DOM: Workers component. This vulnerability was fixed in Firefox 151, Firefox ESR 140.11, Thunderbird 151, and Thunderbird 140.11.

CVSS v3
8.8
EG Score
6.5(medium)
EPSS
30.6%
KEV
Not listed

Published

May 19, 2026

Last Modified

May 20, 2026

Advisory Details (5)

Auto-updated May 20, 2026
No patch confirmed yet.
generic

Security Vulnerabilities fixed in Thunderbird 140.11 — Mozilla

https://www.mozilla.org/security/advisories/mfsa2026-51/
generic

Security Vulnerabilities fixed in Thunderbird 151 — Mozilla

https://www.mozilla.org/security/advisories/mfsa2026-50/
generic

Security Vulnerabilities fixed in Firefox ESR 140.11 — Mozilla

https://www.mozilla.org/security/advisories/mfsa2026-48/
generic

Security Vulnerabilities fixed in Firefox 151 — Mozilla

https://www.mozilla.org/security/advisories/mfsa2026-46/
generic

Access Denied

https://bugzilla.mozilla.org/show_bug.cgi?id=2031064

Vendor Advisories for CVE-2026-8955(20)

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

Patch Availability(21)

Vendor / EcosystemFixed in / PatchReleasedSource
redhatfirefox-0:140.11.0-1.el10_02026-06-22redhat
redhatfirefox-0:140.11.0-1.el9_22026-06-17redhat
redhatfirefox-0:140.11.0-1.el9_62026-06-17redhat
redhatthunderbird-0:140.11.0-1.el9_62026-06-17redhat
redhatthunderbird-0:140.11.0-1.el10_02026-06-17redhat
redhatfirefox-0:140.11.0-1.el9_42026-06-17redhat
redhatfirefox-0:140.11.0-1.el8_82026-06-17redhat
redhatthunderbird-0:140.11.0-1.el8_62026-06-17redhat
redhatfirefox-0:140.11.0-1.el8_62026-06-17redhat
redhatfirefox-0:140.11.0-1.el8_42026-06-17redhat
redhatfirefox-0:140.11.0-1.el7_92026-06-17redhat
redhatthunderbird-0:140.11.0-1.el9_42026-06-16redhat
redhatthunderbird-0:140.11.0-1.el8_82026-06-16redhat
redhatthunderbird-0:140.11.0-1.el9_22026-06-16redhat
redhatthunderbird-0:140.11.0-1.el8_42026-06-16redhat
redhatthunderbird-0:140.11.0-1.el8_102026-06-03redhat
redhatthunderbird-0:140.11.0-1.el10_22026-06-01redhat
redhatthunderbird-0:140.11.0-1.el9_82026-05-27redhat
redhatfirefox-0:140.11.0-1.el9_82026-05-27redhat
redhatfirefox-0:140.11.0-1.el8_102026-05-27redhat
redhatfirefox-0:140.11.0-1.el10_22026-05-27redhat

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

(1)

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 9× in last 7d / 82× 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 120 total refreshes for this CVE.

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

Frequently asked(5)

What is CVE-2026-8955?
CVE-2026-8955 is a high vulnerability published on May 19, 2026. Privilege escalation in the DOM: Workers component. This vulnerability was fixed in Firefox 151, Firefox ESR 140.11, Thunderbird 151, and Thunderbird 140.11.
When was CVE-2026-8955 disclosed?
CVE-2026-8955 was first published in the National Vulnerability Database on May 19, 2026, with the most recent update on May 20, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-8955 actively exploited?
CVE-2026-8955 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-2026-8955?
CVE-2026-8955 has a CVSS v3 base score of 8.8 (NVD). EchelonGraph synthesises NVD + CISA KEV + FIRST EPSS + GHSA into a combined EG score of 6.5.
How do I remediate CVE-2026-8955?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-8955, 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-2026-8955

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