CVE-2026-2786

Mozilla Firefox use-after-free

9.8 CRITICALEPSS 0.45%

Published24 Feb 2026

Description

Use-after-free in the JavaScript Engine component. This vulnerability was fixed in Firefox 148, Firefox ESR 140.8, Thunderbird 148, and Thunderbird 140.8.

CVSS 3.1 breakdown

Attack vectorNetwork

Attack complexityLow

Privileges requiredNone

User interactionNone

ScopeUnchanged

ConfidentialityHigh

IntegrityHigh

AvailabilityHigh

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Affected products

Mozilla Firefox< 148.0 · < 140.8.0

Mozilla Thunderbird< 148.0 · < 140.8.0

Remediation

Fixed in

Mozilla Firefox≥ 148.0

Mozilla Thunderbird≥ 148.0

Patch & vendor advisories

References

https://bugzilla.mozilla.org/show_bug.cgi?id=2013612Issue TrackingPermissions Required
https://www.mozilla.org/security/advisories/mfsa2026-13/Vendor Advisory
https://www.mozilla.org/security/advisories/mfsa2026-15/Vendor Advisory
https://www.mozilla.org/security/advisories/mfsa2026-16/Vendor Advisory
https://www.mozilla.org/security/advisories/mfsa2026-17/Vendor Advisory

Related CVEs

Recent high-severity vulnerabilities sharing a weakness type.

Frequently asked

Is CVE-2026-2786 being actively exploited?

CVE-2026-2786 is not in the CISA KEV catalog. Its EPSS exploit probability is 0.45%.

How severe is CVE-2026-2786?

CVE-2026-2786 has a CVSS 3.1 base score of 9.8, rated critical. EPSS estimates a 0.45% probability of exploitation.

Which products are affected by CVE-2026-2786?

Affected products include Mozilla Firefox, Mozilla Thunderbird.

How do I fix CVE-2026-2786?

Upgrade affected software to a fixed version, for example Mozilla Firefox 148.0, Mozilla Thunderbird 148.0 or later, then confirm no affected versions remain in your inventory.

How Secuno handles this

Secuno correlates vulnerabilities like CVE-2026-2786 against the real software inventory on every managed device, as each hourly inventory arrives. Rather than a static severity, each match is scored in context: exploit availability, EPSS, the asset's exposure, and business criticality decide where it lands in the queue. If an affected version is present anywhere across your portfolio, it surfaces automatically with a prioritised remediation path.

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Data from the NVD, CISA KEV catalog and FIRST EPSS. CVSS 3.1 base score shown where available.