CVE-2026-74988

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: 0%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 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 153.1, Thunderbird 154, 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%
Exploitation0% × 40%
Automatability100% × 15%
Action: Routine — remediate on your standard cadence.
EPSS PROB
0%
EPSS %ILE
5%
KEV
Not listed

Published

August 18, 2026

Last Modified

August 20, 2026

Advisory Details (7)

Auto-updated Aug 20, 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 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 154 — Mozilla

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

Client Challenge

https://bugzilla.mozilla.org/buglist.cgi?bug_id=2053153%2C2053262%2C2054763%2C2059198%2C2059224
generic

Client Challenge

https://bugzilla.mozilla.org/buglist.cgi?bug_id=2045796%2C2046734%2C2051424%2C2054721%2C2057994%2C2058094%2C2058611%2C2058615%2C2058616%2C2061315
generic

Client Challenge

https://bugzilla.mozilla.org/buglist.cgi?bug_id=2018164%2C2045404%2C2045507%2C2045711%2C2052403%2C2053174%2C2054643%2C2054667%2C2054671%2C2054674%2C2054687%2C2054717%2C2054761%2C2054787%2C2055676%2C2056779%2C2056781%2C2058629%2C2059019%2C2059138

Vendor Advisories for CVE-2026-74988(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 19× in last 7d / 19× 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 07:14 UTCGHSA enrichment
  2. 2026-08-21 03:29 UTCGHSA enrichment
  3. 2026-08-20 23:44 UTCEG score recompute
  4. 2026-08-20 23:44 UTCGHSA enrichment
  5. 2026-08-20 22:56 UTCEPSS rescore
  6. 2026-08-20 20:00 UTCEG score recompute
  7. 2026-08-20 20:00 UTCGHSA enrichment
  8. 2026-08-20 18:18 UTCGHSA enrichment
  9. 2026-08-20 17:32 UTCEG score recompute▲ 9.80
  10. 2026-08-20 17:32 UTCGHSA enrichment
  11. 2026-08-20 17:31 UTCMITRE cvelistV5CVSS v3 → 9.8 · severity → CRITICAL
  12. 2026-08-19 17:04 UTCEPSS rescore
  13. 2026-08-18 19:24 UTCGHSA enrichment
  14. 2026-08-18 19:23 UTCNVD update
  15. 2026-08-18 19:05 UTCGHSA enrichment
  16. 2026-08-18 19:04 UTCMITRE cvelistV5
  17. 2026-08-18 13:19 UTCNVD update
  18. 2026-08-18 12:42 UTCEG score recompute
  19. 2026-08-18 12:41 UTCMITRE cvelistV5first tracked

Frequently asked(5)

What is CVE-2026-74988?
CVE-2026-74988 is a critical vulnerability published on August 18, 2026. Internally found bugs present in 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,…
When was CVE-2026-74988 disclosed?
CVE-2026-74988 was first published in the National Vulnerability Database on August 18, 2026, with the most recent update on August 20, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-74988 actively exploited?
CVE-2026-74988 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 94.9% of all scored CVEs.
What is the CVSS score of CVE-2026-74988?
CVE-2026-74988 has a CVSS v3.1 base score of 9.8 (CISA-ADP / Vulnrichment enrichment; NVD's own analysis pending).
How do I remediate CVE-2026-74988?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-74988, 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-2026-74988

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