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CVE-2026-74943

Mozilla Firefox, Thunderbird, firefox

Use-after-free in the Graphics: ImageLib component. This vulnerability was fixed in Firefox 154, Firefox ESR 115.39, Firefox ESR 140.14, Firefox ESR 153.1, Thunderbird 154, Thunderbird 140.14, and Thunderbird 153.1.

CVSS
9.8
EPSS
-
- percentile
CISA KEV
Not listed
Published
2026.08.18
PRIORITY ASSESSMENT

Review

The CVSS severity warrants an early asset and exposure review.

Known exploitationNot established by KEV
Exploit probability-
Technical severityCVSS 9.8

Vulnerability overview

Use-after-free in the Graphics: ImageLib component. This vulnerability was fixed in Firefox 154, Firefox ESR 115.39, Firefox ESR 140.14, Firefox ESR 153.1, Thunderbird 154, Thunderbird 140.14, and Thunderbird 153.1.

Affected product and versions

Product
Mozilla Firefox, Thunderbird, firefox
Affected versions
< 115.39.0, >= 116.0 < 140.14.0, >= 141.0 < 153.1.0
Fixed versions
Verify the fixed release separately for each affected product line

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:H/I:H/A:H
CWE
CWE-416