CVE-2026-8955

HIGHNVD 8.88.8—
EchelonGraph scoreMEDIUM confidence

This high-severity CVE scores 8.8 under NVD CVSS v3. EPSS exploit probability: 0.4%, top 68% of all CVEs by exploit prediction. GitHub Security Advisory enrichment pending alignment with NVD CVSS.

Triggered by: NVD CVSS baseline
Sources: epss, ghsa, nvd
8.8EG
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS PROB: 0%CVSS: 8.8Exploit: None knownExposed: 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
8.8(medium)
EG Risk
40(Track)
EG Risk 40/100SSVC: 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
Severity88% × 45%
Exploitation0% × 40%
Automatability0% × 15%
Action: Routine — remediate on your standard cadence.
EPSS PROB
0%
EPSS %ILE
33%
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.

Affected Packages

(8 across 4 ecosystems)
Debian:11(2)
PackageVulnerable rangeFixed inDependents
firefox-esr102.1.0esr-1 ... 91.9.1esr-1~deb9u1 (275 versions)140.11.0esr-1~deb11u1—
thunderbird1:102.0.1-1 ... 1:91.9.0-1~deb9u1 (326 versions)1:140.11.0esr-1~deb11u1—
Debian:12(2)
PackageVulnerable rangeFixed inDependents
firefox-esr102.11.0esr-1 ... 140.9.1esr-1~deb13u1 (182 versions)140.11.0esr-1~deb12u1—
thunderbird1:102.11.0-1 ... 1:140.9.1esr-1~deb13u1 (211 versions)1:140.11.0esr-1~deb12u1—
Debian:13(2)
PackageVulnerable rangeFixed inDependents
firefox-esr128.13.0esr-1 ... 140.9.1esr-1~deb13u1 (58 versions)140.11.0esr-1~deb13u1—
thunderbird1:128.13.0esr-1 ... 1:140.9.1esr-1~deb13u1 (67 versions)1:140.11.0esr-1~deb13u1—
Debian:14(2)
PackageVulnerable rangeFixed inDependents
firefox-esr128.13.0esr-1 ... 140.9.1esr-1~deb13u1 (59 versions)140.11.0esr-1—
thunderbird1:128.13.0esr-1 ... 1:140.9.1esr-1~deb13u1 (68 versions)1:140.11.0esr-1—

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

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 0% probability of exploitation in the next 30 days, which ranks it in the top 67.5% of all scored CVEs.
What is the CVSS score of CVE-2026-8955?
CVE-2026-8955 has a CVSS v3 base score of 8.8 (NVD).
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

See which npm, PyPI, Go, and Maven packages are affected by CVE-2026-8955

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