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Review reviewHigh

CVE-2026-12305

Mozilla Firefox, Thunderbird, firefox

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

CVSS
7.5
EPSS
0.37%
30.1% percentile
CISA KEV
Not listed
Published
2026.06.16
PRIORITY ASSESSMENT

Review review

The CVSS severity warrants an early asset and exposure review.

Known exploitationNot established by KEV
Exploit probability0.37%
Technical severityCVSS 7.5

Vulnerability overview

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

Affected product and versions

Product
Mozilla Firefox, Thunderbird, firefox
Affected versions
< 140.12.0, < 152.0.0
Fixed versions
140.12.0, 152.0.0

Recommended response sequence

Confirm exposure before applying a vendor-supported change.

Full remediation guide
  1. 1
    Identify

    Confirm that Mozilla Firefox, Thunderbird, firefox and an affected version are present.

  2. 2
    Prioritize

    Combine exploitation signals with asset exposure and business criticality.

  3. 3
    Remediate

    Follow the vendor advisory or supported update path and preserve rollback options.

  4. 4
    Verify

    Recheck the version, service health, access paths, and relevant logs.

Technical data

CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
CWE
CWE-119
CVE-2026-12305 — Mozilla Firefox, Thunderbird, firefox | SECUFOCUS NOW