High 8.1Published Jun 16, 2026

CVE-2026-12327Memory safety bugs fixed in Firefox ESR 140.12, Thunderbird ESR 140.12, Firefox 152 and Thunderbird 152

Updated under an hour ago (Oct 28, 2026, 8:40 AM ET)

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It affects Mozilla Firefox and 1 other product. Add what you run to find out whether that includes you.

No exploitation reported and no EPSS estimate yet.

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Exploited in the last 30 days

Memory safety bugs present in Firefox ESR 140.11, Thunderbird ESR 140.11, Firefox 151 and Thunderbird 151. Some of these bugs showed evidence of memory corruption and we presume that with enough effort some of these could have been exploited to run arbitrary code. This vulnerability was fixed in Firefox 152, Firefox ESR 140.12, Thunderbird 152, and Thunderbird 140.12.

CVSS: 8.1 HIGH (v3.1, CISA ADP)CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H
Weakness (CWE): CWE-119
Known exploited: Not in CISA's KEV catalog
EPSS (exploitation in the next 30 days): Not loaded for this CVE
Assigned by: mozilla
NVD analysis: Analyzed
Record last updated: Jun 17, 2026
First seen by InfoSec Signals: Oct 9, 2026

Affected products

Affected products

Mozilla Firefox mozilla:firefox (from the name)	140.12 builds before 140.* not affected; from 152 not affected	CNA record
Mozilla Thunderbird mozilla:thunderbird (from the name)	140.12 builds before 140.* not affected; from 152 not affected	CNA record
mozilla firefox mozilla:firefox	before 115.37.0; before 152.0.0; from 140.0 before 140.12.0	NVD
mozilla thunderbird mozilla:thunderbird	before 152.0.0; from 140.0 before 140.12.0	NVD

References

References

https://bugzilla.mozilla.org/buglist.cgi?bug_id=2011842%2C2023902%2C2025512%2C2027312%2C2029444%2C2036571%2C2036900%2C2036936%2C2037995%2C2038551%2C2040717%2C2042724	broken-link
https://www.mozilla.org/security/advisories/mfsa2026-57/	vendor-advisory
https://www.mozilla.org/security/advisories/mfsa2026-58/	vendor-advisory
https://www.mozilla.org/security/advisories/mfsa2026-60/	vendor-advisory
https://www.mozilla.org/security/advisories/mfsa2026-61/	vendor-advisory

The CVE record on cve.org NVD's entry

The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.