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Vulnerabilities

Vulnerability · CVE-2026-12307

Memory safety bug fixed in Thunderbird 152.

Published Jun 16, 2026 · catalog updated Oct 21, 2026 · Memory safety bug fixed

Last checked Oct 26, 2026. A connected source was read within the last 7 days.

Check if you run it

No confirmed exploitation is on record for CVE-2026-12307. EPSS is 0.26%. Act only if a listed version of Memory safety bug fixed is installed.

Gaps on this record

  • The stored product name is a package slug. The name on this page is taken from the title (Memory safety bug fixed).
  • No vendor fix or required action is stored. Compare the linked advisory before you change production.

Same product and reporting

Severity
Medium5.3
Known exploitation
Not in CISA/VulnCheck KEV
EPSS
0.26%
Remediation
Version ranges on file
Affected products
cpe mozilla/firefox · cpe mozilla/thunderbird

Memory safety bug fixed in Thunderbird 152. This vulnerability was fixed in Firefox 152, Firefox ESR 140.12, Thunderbird 152, and Thunderbird 140.12.

Are you affected?

Enter the version you run. The result uses only the ranges stored on this record.

The check returns affected, not affected, or incomplete. It does not guess a version that is missing from the record.

  • cpe mozilla/firefox< 140.12.0
  • cpe mozilla/firefox< 152.0.0
  • cpe mozilla/thunderbird< 140.12.0
  • cpe mozilla/thunderbird< 152.0.0

How to fix CVE-2026-12307

What to do

Three questions, each answered from this record only. Confirm the vendor advisory before you patch.

Should you patch?

No confirmed exploitation is on record for CVE-2026-12307. EPSS is 0.26%. Act only if a listed version of Memory safety bug fixed is installed.

Which versions are affected?

Compare what you have installed with < 140.12.0, < 152.0.0. Compare the installed version with the linked vendor advisory before you change production.

What should an analyst verify?

CWE-119: Buffer Overflow. EPSS 0.26%. There is no CISA KEV listing. No Exploit-DB or Metasploit reference is linked. Use the source links for the original advisory.

Code

The project this record applies to. Exploit listings stay in References.

No public source repository is identified for this product.

Timeline

Detection, updates, and resolution for this record.

  1. Jun 16, 2026 · NIST NVD

    Detected

    Memory safety bug fixed in Thunderbird 152. This vulnerability was fixed in Firefox 152, Firefox ESR 140.12, Thunderbird 152, and Thunderbird 140.12.

  2. Oct 21, 2026 · NIST NVD

    Updated

    Memory safety bug fixed in Thunderbird 152. This vulnerability was fixed in Firefox 152, Firefox ESR 140.12, Thunderbird 152, and Thunderbird 140.12.

Sources

  • CVE.orgVulnerability recordCVE-2026-12307

    Official CVE identifier

    cve.org
  • FIRST EPSSExploitation probabilityCVE-2026-12307

    30-day exploitation probability 0.26%

    first.org
  • NIST NVDVulnerability recordCVE-2026-12307

    Memory safety bug fixed in Thunderbird 152. This vulnerability was fixed in Firefox 152, Firefox ESR 140.12, Thunderbird 152, and Thunderbird 140.12.

    nvd.nist.gov

References

Freshness

Last verified in this catalog Oct 26, 2026. Significant claims (KEV, EPSS, CVSS, affected ranges) come from the source rows above — open the original publisher for the authoritative advisory.

  • FIRST EPSSOct 23, 2026
  • CVE.orgOct 21, 2026
  • NIST NVDOct 21, 2026