CVE-2026-74990

CRITICALPre-NVD 9.89.8—
EchelonGraph scoreHIGH confidence

Score 9.8 from GitHub Security Advisory (severity: CRITICAL) published 2026-08-18. CISA-ADP (Vulnrichment) CVSS v3.1 baseline 9.8; sources differ by 0.0.

Triggered by: GitHub Security Advisory CVSS
Sources: cisa-adp, epss, ghsa
Trending — 5 sources updated this week
9.8EG
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS PROB: 1%CVSS: 9.8Exploit: None knownExposed: 0

No vendor fix yet — apply a workaround or compensating control (WAF / firewall / segmentation) and watch for a patch.

Internally found bugs present in Thunderbird ESR 140.13, Thunderbird ESR 153.0 and Thunderbird 153. Some of these bugs showed evidence of memory corruption or another security-relevant defect and we presume that with enough effort some of these could have been exploited. This vulnerability was fixed in Firefox 154, Firefox ESR 115.39, Firefox ESR 140.14, Firefox ESR 153.1, Thunderbird 154, Thunderbird 140.14, and Thunderbird 153.1.

CVSS v3
9.8
EG Score
9.8(high)
EG Risk
59(Track)
EG Risk 59/100SSVC: 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
Severity98% × 45%
Exploitation1% × 40%
Automatability100% × 15%
Action: Routine — remediate on your standard cadence.
EPSS PROB
1%
EPSS %ILE
42%
KEV
Not listed

Published

August 18, 2026

Last Modified

August 19, 2026

Advisory Details (9)

Auto-updated Aug 19, 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 ESR 115.39 — Mozilla

https://www.mozilla.org/security/advisories/mfsa2026-75/
generic

Security Vulnerabilities fixed in Firefox 154 — Mozilla

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

Client Challenge

https://bugzilla.mozilla.org/buglist.cgi?bug_id=2045774%2C2048490%2C2050864%2C2053159%2C2053260%2C2053261%2C2053582%2C2053599%2C2053607%2C2053608%2C2053853%2C2054626%2C2054627%2C2054635%2C2054677%2C2054740%2C2054832%2C2056792%2C2057098%2C2057100%2C2057101%2C2057103%2C2057117%2C2057118%2C2058048%2C2058049%2C2058622%2C2058623%2C2058665%2C2058666%2C2059121%2C2059164%2C2059188
generic

Client Challenge

https://bugzilla.mozilla.org/buglist.cgi?bug_id=2045762%2C2052401%2C2058208

Vendor Advisories for CVE-2026-74990(1)

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

Weakness Classification(1)

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

Data Freshness Timeline

(refreshed 32× in last 7d / 32× 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.

  1. 2026-08-21 08:58 UTCGHSA enrichment
  2. 2026-08-21 05:11 UTCGHSA enrichment
  3. 2026-08-21 01:23 UTCEG score recompute
  4. 2026-08-21 01:23 UTCGHSA enrichment
  5. 2026-08-20 22:56 UTCEPSS rescore
  6. 2026-08-20 21:36 UTCGHSA enrichment
  7. 2026-08-20 17:49 UTCGHSA enrichment
  8. 2026-08-20 14:01 UTCGHSA enrichment
  9. 2026-08-20 09:45 UTCGHSA enrichment
  10. 2026-08-20 05:58 UTCGHSA enrichment
  11. 2026-08-20 02:11 UTCGHSA enrichment
  12. 2026-08-19 22:23 UTCGHSA enrichment
  13. 2026-08-19 18:35 UTCEG score recompute
  14. 2026-08-19 18:35 UTCGHSA enrichment
  15. 2026-08-19 17:04 UTCEPSS rescore
  16. 2026-08-19 14:46 UTCGHSA enrichment
  17. 2026-08-19 11:37 UTCGHSA enrichment
  18. 2026-08-19 07:50 UTCGHSA enrichment
  19. 2026-08-19 04:02 UTCGHSA enrichment
  20. 2026-08-19 00:12 UTCEG score recompute
  21. 2026-08-19 00:12 UTCGHSA enrichment
  22. 2026-08-18 20:24 UTCGHSA enrichment
  23. 2026-08-18 19:45 UTCEG score recompute▲ 9.80
  24. 2026-08-18 19:45 UTCGHSA enrichment
  25. 2026-08-18 19:43 UTCMITRE cvelistV5CVSS v3 → 9.8 · severity → CRITICAL
Show 7 more
  1. 2026-08-18 19:25 UTCGHSA enrichment
  2. 2026-08-18 19:23 UTCNVD update
  3. 2026-08-18 19:06 UTCGHSA enrichment
  4. 2026-08-18 19:04 UTCMITRE cvelistV5
  5. 2026-08-18 13:19 UTCNVD update
  6. 2026-08-18 12:42 UTCEG score recompute
  7. 2026-08-18 12:41 UTCMITRE cvelistV5first tracked

Related CVEs(same CWE)

Frequently asked(5)

What is CVE-2026-74990?
CVE-2026-74990 is a critical vulnerability published on August 18, 2026. Internally found bugs present in Thunderbird ESR 140.13, Thunderbird ESR 153.0 and Thunderbird 153. Some of these bugs showed evidence of memory corruption or another security-relevant defect and we presume that with enough effort some of these could have been exploited. This vulnerability was…
When was CVE-2026-74990 disclosed?
CVE-2026-74990 was first published in the National Vulnerability Database on August 18, 2026, with the most recent update on August 19, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-74990 actively exploited?
CVE-2026-74990 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 1% probability of exploitation in the next 30 days, which ranks it in the top 57.8% of all scored CVEs.
What is the CVSS score of CVE-2026-74990?
CVE-2026-74990 has a CVSS v3.1 base score of 9.8 (CISA-ADP / Vulnrichment enrichment; NVD's own analysis pending).
How do I remediate CVE-2026-74990?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-74990, 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-2026-74990

Explore →

Is Your Infrastructure Affected by CVE-2026-74990?

EchelonGraph automatically scans your cloud infrastructure and maps CVE exposure using blast radius analysis.

Start Free Scan →Browse All CVEs