CVE-2026-74959

CRITICALPre-NVD 9.19.1—
EchelonGraph scoreMEDIUM confidence

Score 9.1 from GitHub Security Advisory (severity: CRITICAL) published 2026-08-18. CISA-ADP (Vulnrichment) CVSS v3.1 baseline 9.1; sources differ by 0.0.

Triggered by: GitHub Security Advisory CVSS
Sources: cisa-adp, epss, ghsa
Trending — 4 sources updated this week
9.1EG
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS PROB: 0%CVSS: 9.1Exploit: None knownExposed: 0

A fix is available — apply it.

Mitigation bypass in the Storage: Cache API component. This vulnerability was fixed in Firefox 154, Firefox ESR 140.14, Firefox ESR 153.1, Thunderbird 154, Thunderbird 140.14, and Thunderbird 153.1.

CVSS v3
9.1
EG Score
9.1(medium)
EG Risk
56(Track)
EG Risk 56/100SSVC: 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
Severity91% × 45%
Exploitation0% × 40%
Automatability100% × 15%
Action: Routine — remediate on your standard cadence.
EPSS PROB
0%
EPSS %ILE
28%
KEV
Not listed

Published

August 18, 2026

Last Modified

August 24, 2026

Advisory Details (7)

Auto-updated Sep 15, 2026
No patch confirmed yet.
generic

Security Vulnerabilities fixed in Thunderbird 153.1 — Mozilla

https://www.mozilla.org/security/advisories/mfsa2026-80/
generic

Security Vulnerabilities fixed in Thunderbird 140.14 — Mozilla

https://www.mozilla.org/security/advisories/mfsa2026-79/
generic

Security Vulnerabilities fixed in Thunderbird 154 — Mozilla

https://www.mozilla.org/security/advisories/mfsa2026-78/
generic

Security Vulnerabilities fixed in Firefox ESR 153.1 — Mozilla

https://www.mozilla.org/security/advisories/mfsa2026-77/
generic

Security Vulnerabilities fixed in Firefox ESR 140.14 — Mozilla

https://www.mozilla.org/security/advisories/mfsa2026-76/
generic

Security Vulnerabilities fixed in Firefox 154 — Mozilla

https://www.mozilla.org/security/advisories/mfsa2026-74/
generic

Access Denied

https://bugzilla.mozilla.org/show_bug.cgi?id=2047853

Vendor Advisories for CVE-2026-74959(16)

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
redhatthunderbird-0:140.14.0-1.el8_62026-09-09redhat
redhatfirefox-0:140.14.0-1.el9_22026-09-09redhat
redhatthunderbird-0:140.14.0-1.el8_82026-09-09redhat
redhatthunderbird-0:140.14.0-1.el9_22026-09-09redhat
redhatthunderbird-0:140.14.0-1.el8_42026-09-09redhat
redhatthunderbird-0:140.14.0-1.el9_42026-09-08redhat
redhatfirefox-0:140.14.0-1.el8_62026-09-08redhat
redhatfirefox-0:140.14.0-1.el9_62026-09-08redhat
redhatthunderbird-0:140.14.0-1.el9_82026-09-08redhat
redhatfirefox-0:140.14.0-1.el7_92026-09-08redhat
redhatthunderbird-0:140.14.0-1.el10_22026-09-08redhat
redhatfirefox-0:140.14.0-1.el10_02026-09-08redhat
redhatfirefox-0:140.14.0-1.el8_82026-09-08redhat
redhatthunderbird-0:140.14.0-1.el10_02026-09-08redhat
redhatthunderbird-0:140.14.0-1.el8_102026-09-08redhat
redhatfirefox-0:140.14.0-1.el8_42026-09-08redhat
redhatfirefox-0:140.14.0-1.el9_42026-09-08redhat
redhatthunderbird-0:140.14.0-1.el9_62026-09-08redhat
redhatfirefox-0:140.14.0-1.el10_22026-08-24redhat
redhatfirefox-0:140.14.0-1.el9_82026-08-24redhat
redhatfirefox-0:140.14.0-1.el8_102026-08-24redhat

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

(6 across 3 ecosystems)
Debian:12(2)
PackageVulnerable rangeFixed inDependents
firefox-esr102.11.0esr-1 ... 140.9.1esr-1~deb13u1 (195 versions)140.14.0esr-1~deb12u1—
thunderbird1:102.11.0-1 ... 1:140.9.1esr-1~deb13u1 (224 versions)1:140.14.0esr-1~deb12u1—
Debian:13(2)
PackageVulnerable rangeFixed inDependents
firefox-esr128.13.0esr-1 ... 140.9.1esr-1~deb13u1 (71 versions)140.14.0esr-1~deb13u1—
thunderbird1:128.13.0esr-1 ... 1:140.9.1esr-1~deb13u1 (80 versions)1:140.14.0esr-1~deb13u1—
Debian:14(2)
PackageVulnerable rangeFixed inDependents
firefox-esr128.13.0esr-1 ... 140.9.1esr-1~deb13u1 (72 versions)140.14.0esr-2—
thunderbird1:128.13.0esr-1 ... 1:140.9.1esr-1~deb13u1 (81 versions)1:140.14.0esr-1—

Weakness Classification(1)

MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.

Additional Vendor Advisories

(6)

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 87× in last 7d / 343× 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 351 total refreshes for this CVE.

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

Frequently asked(5)

What is CVE-2026-74959?
CVE-2026-74959 is a critical vulnerability published on August 18, 2026. Mitigation bypass in the Storage: Cache API component. This vulnerability was fixed in Firefox 154, Firefox ESR 140.14, Firefox ESR 153.1, Thunderbird 154, Thunderbird 140.14, and Thunderbird 153.1.
When was CVE-2026-74959 disclosed?
CVE-2026-74959 was first published in the National Vulnerability Database on August 18, 2026, with the most recent update on August 24, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-74959 actively exploited?
CVE-2026-74959 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 72.2% of all scored CVEs.
What is the CVSS score of CVE-2026-74959?
CVE-2026-74959 has a CVSS v3.1 base score of 9.1 (CISA-ADP / Vulnrichment enrichment; NVD's own analysis pending).
How do I remediate CVE-2026-74959?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-74959, 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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