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: 0.5%CVSS: 9.1Exploit: None knownExposed services: Not assessed

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
9.1CRITICALmedium confidence
EG Risk
56
EG Risk 56/100CISA SSVC

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%
CISA SSVC: Track at low or medium mission impact; Attend at high (mission-essential systems).
Action: A fix is available. Apply it within your standard update timelines at low or medium mission impact and sooner than that at high.
EPSS PROB
0.5%
EPSS %ILE
39th
KEV
Not listed

CISA SSVCTrack at low or medium mission impact; Attend at high (mission-essential systems).

A fix is available. Apply it within your standard update timelines at low or medium mission impact and sooner than that at high.

Exploitation none (CISA Vulnrichment) · Automatable yes (CISA Vulnrichment) · Technical impact total (CISA Vulnrichment). Mission impact is CISA's Mission & Well-being decision point, and only you can judge it: high means the affected system is essential to your organisation's mission, or its compromise could cause irreversible harm to people. CISA's decision table

Published

August 18, 2026

Last Modified

August 24, 2026

Advisory Details (7)

Auto-updated Sep 15, 2026
Patch available.
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 / EcosystemFix (by version range) / 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
redhatfirefox-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
redhatfirefox-0:140.14.0-1.el8_82026-09-08redhat
redhatthunderbird-0:140.14.0-1.el9_42026-09-08redhat
redhatfirefox-0:140.14.0-1.el8_42026-09-08redhat
redhatthunderbird-0:140.14.0-1.el10_02026-09-08redhat
redhatfirefox-0:140.14.0-1.el10_02026-09-08redhat
redhatthunderbird-0:140.14.0-1.el8_102026-09-08redhat
redhatthunderbird-0:140.14.0-1.el9_62026-09-08redhat
redhatthunderbird-0:140.14.0-1.el10_22026-09-08redhat
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 rangeFix by version rangeDependents
firefox-esr102.11.0esr-1 ... 140.9.1esr-1~deb13u1 (195 versions)
  • every version up to 140.14.0esr-1~deb12u1: fixed in 140.14.0esr-1~deb12u1
—
thunderbird1:102.11.0-1 ... 1:140.9.1esr-1~deb13u1 (224 versions)
  • every version up to 1:140.14.0esr-1~deb12u1: fixed in 1:140.14.0esr-1~deb12u1
—
Debian:13(2)
PackageVulnerable rangeFix by version rangeDependents
firefox-esr128.13.0esr-1 ... 140.9.1esr-1~deb13u1 (71 versions)
  • every version up to 140.14.0esr-1~deb13u1: fixed in 140.14.0esr-1~deb13u1
—
thunderbird1:128.13.0esr-1 ... 1:140.9.1esr-1~deb13u1 (80 versions)
  • every version up to 1:140.14.0esr-1~deb13u1: fixed in 1:140.14.0esr-1~deb13u1
—
Debian:14(2)
PackageVulnerable rangeFix by version rangeDependents
firefox-esr128.13.0esr-1 ... 140.9.1esr-1~deb13u1 (72 versions)
  • every version up to 140.14.0esr-2: fixed in 140.14.0esr-2
—
thunderbird1:128.13.0esr-1 ... 1:140.9.1esr-1~deb13u1 (81 versions)
  • every version up to 1:140.14.0esr-1: fixed in 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 61× in last 7d / 320× 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 504 total refreshes for this CVE.

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

Related CVEs(same vendor + same CWE)

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 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 0.5% probability of exploitation in the next 30 days (39th percentile of EPSS-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?
A fix for CVE-2026-74959 is available: update to the fixed version the vendor names in its advisory. The vendor advisories EchelonGraph has for CVE-2026-74959 are linked in the Vendor Advisories panel on this page.

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