CVE-2026-6766

HIGHPre-NVD 7.57.5—
EchelonGraph scoreMEDIUM confidence

Score 7.5 from GitHub Security Advisory (severity: HIGH) published 2026-04-21. the CNA's CVSS baseline 7.5; sources differ by 0.0.

Triggered by: GitHub Security Advisory CVSS
Sources: cna:mozilla, epss, ghsa
7.5
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS: 0%CVSS: 7.5Exploit: NoneExposed: 0

A fix is available — apply it.

Incorrect boundary conditions in the Libraries component in NSS. This vulnerability was fixed in Firefox 150, Firefox ESR 140.10, Thunderbird 150, and Thunderbird 140.10.

CVSS v3
7.5
EG Score
7.5(medium)
EG Risk
49(Track)
EG Risk 49/100SSVC: 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
Severity75% × 45%
Exploitation0% × 40%
Automatability100% × 15%
Action: Routine — remediate on your standard cadence.
EPSS
17.3%
KEV
Not listed

Published

April 21, 2026

Last Modified

May 26, 2026

Advisory Details (5)

Auto-updated Jun 7, 2026
No patch confirmed yet.
generic

Security Vulnerabilities fixed in Thunderbird 140.10 — Mozilla

https://www.mozilla.org/security/advisories/mfsa2026-34/
generic

Security Vulnerabilities fixed in Thunderbird 150 — Mozilla

https://www.mozilla.org/security/advisories/mfsa2026-33/
generic

Security Vulnerabilities fixed in Firefox ESR 140.10 — Mozilla

https://www.mozilla.org/security/advisories/mfsa2026-32/
generic

Security Vulnerabilities fixed in Firefox 150 — Mozilla

https://www.mozilla.org/security/advisories/mfsa2026-30/
generic

Access Denied

https://bugzilla.mozilla.org/show_bug.cgi?id=2023207

Vendor Advisories for CVE-2026-6766(20)

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

Patch Availability(27)

Vendor / EcosystemFixed in / PatchReleasedSource
redhatfirefox-0:140.10.0-1.el8_42026-05-20redhat
redhatthunderbird-0:140.10.0-1.el10_02026-05-20redhat
redhatthunderbird-0:140.10.0-1.el8_82026-05-20redhat
redhatthunderbird-0:140.10.0-1.el9_62026-05-20redhat
redhatthunderbird-0:140.10.0-1.el9_02026-05-20redhat
redhatthunderbird-0:140.10.0-1.el9_22026-05-20redhat
redhatthunderbird-0:140.10.0-1.el8_42026-05-20redhat
redhatthunderbird-0:140.10.0-1.el8_62026-05-20redhat
redhatfirefox-0:140.10.0-1.el8_62026-05-20redhat
redhatfirefox-0:140.10.0-1.el9_42026-05-20redhat
redhatthunderbird-0:140.10.0-1.el9_42026-05-20redhat
redhatfirefox-0:140.10.0-2.el7_92026-05-20redhat
redhatfirefox-0:140.10.0-1.el9_82026-05-19redhat
redhatfirefox-0:140.10.0-1.el10_22026-05-19redhat
redhatthunderbird-0:140.10.1-1.el9_82026-05-19redhat
redhatthunderbird-0:140.10.0-1.el10_22026-05-19redhat
redhatfirefox-0:140.10.0-1.el9_02026-05-14redhat
redhatfirefox-0:140.10.0-1.el9_62026-05-14redhat
redhatfirefox-0:140.10.0-1.el10_02026-05-14redhat
redhatfirefox-0:140.10.0-1.el8_82026-05-14redhat
redhatfirefox-0:140.10.0-1.el9_22026-05-14redhat
redhatthunderbird-0:140.10.0-1.el9_72026-05-11redhat
redhatthunderbird-0:140.10.0-1.el8_102026-05-04redhat
redhatthunderbird-0:140.10.0-1.el10_12026-04-30redhat
redhatfirefox-0:140.10.0-1.el9_72026-04-27redhat
redhatfirefox-0:140.10.0-1.el8_102026-04-27redhat
redhatfirefox-0:140.10.0-1.el10_12026-04-27redhat

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

(7)

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 10× in last 7d / 42× 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 130 total refreshes for this CVE.

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

Frequently asked(5)

What is CVE-2026-6766?
CVE-2026-6766 is a high vulnerability published on April 21, 2026. Incorrect boundary conditions in the Libraries component in NSS. This vulnerability was fixed in Firefox 150, Firefox ESR 140.10, Thunderbird 150, and Thunderbird 140.10.
When was CVE-2026-6766 disclosed?
CVE-2026-6766 was first published in the National Vulnerability Database on April 21, 2026, with the most recent update on May 26, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-6766 actively exploited?
CVE-2026-6766 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 17.3% percentile likelihood of exploitation in the next 30 days — higher percentiles indicate greater predicted risk.
What is the CVSS score of CVE-2026-6766?
CVE-2026-6766 has a CVSS v4.0 base score of 7.5 (CNA self-assessment; NVD's own analysis pending).
How do I remediate CVE-2026-6766?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-6766, 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

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