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.
CVE-2026-74959
UNRATEDCVSS · not yet scoredTrending — 5 sources updated this week
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EchelonGraph verdictMonitorLow exploitation likelihood right now — keep watching.
- No CVSS published and no exploitation signals yet
CISA-KEV: Not listedEPSS PROB: 0%CVSS v2: —Exploit: None knownExposed: 0
No vendor fix yet — apply a workaround or compensating control (WAF / firewall / segmentation) and watch for a patch.
- CVSS v3
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- EchelonGraph score
- Not yet assessedNo source has published severity data for this CVE yet — no CVSS score from NVD or a CNA, no GitHub advisory, and it is not in CISA KEV. This is not a rating of zero; we cannot assess it yet.
- EG Score
- —
- EG Risk
- —
- EPSS PROB
- 0%
- EPSS %ILE
- 6%
- KEV
- Not listed
Published
August 18, 2026
Last Modified
August 18, 2026
References (7)
- security@mozillahttps://bugzilla.mozilla.org/show_bug.cgi?id=2047853
- security@mozillahttps://www.mozilla.org/security/advisories/mfsa2026-74/
- security@mozillahttps://www.mozilla.org/security/advisories/mfsa2026-76/
- security@mozillahttps://www.mozilla.org/security/advisories/mfsa2026-77/
- security@mozillahttps://www.mozilla.org/security/advisories/mfsa2026-78/
- security@mozillahttps://www.mozilla.org/security/advisories/mfsa2026-79/
- security@mozillahttps://www.mozilla.org/security/advisories/mfsa2026-80/
Vendor Advisories for CVE-2026-74959(1)
These vendors published their own advisory mentioning this CVE — often with vendor-specific remediation steps + affected product lists not in NVD.
Data Freshness Timeline
(refreshed 9× in last 7d / 9× 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.
- 2026-08-20 22:56 UTCEPSS rescore
- 2026-08-19 17:04 UTCEPSS rescore
- 2026-08-18 19:25 UTCGHSA enrichment
- 2026-08-18 19:23 UTCNVD update
- 2026-08-18 19:06 UTCGHSA enrichment
- 2026-08-18 19:04 UTCMITRE cvelistV5
- 2026-08-18 13:19 UTCNVD update
- 2026-08-18 12:42 UTCEG score recompute
- 2026-08-18 12:41 UTCMITRE cvelistV5first tracked
Frequently asked(4)
What is CVE-2026-74959?
CVE-2026-74959 is a publicly disclosed 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. 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 93.9% of all scored CVEs.
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
Explore the affected products and dependency analysis for CVE-2026-74959
Is Your Infrastructure Affected by CVE-2026-74959?
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