Use-after-free in the CSS Parsing and Computation component. This vulnerability affects Firefox < 149, Firefox ESR < 115.34, Firefox ESR < 140.9, Thunderbird < 149, and Thunderbird < 140.9.

No CVSS v4.0

Attack Vector Network

Attack Complexity Low

Privileges Required None

Scope Unchanged

Confidentiality Impact High

Integrity Impact High

Availability Impact High

User Interaction None

No CVSS v3.0

No CVSS v2

This CVE is not in the KEV list.

No EPSS score available.

Key SSVC decision points have not yet been added.

Default status is the baseline for the product, each version can override it (e.g. patched versions marked unaffected).

Vendor Product Default status Versions
Mozilla Firefox affected
Version Status Constraints
unspecified affected
< 149
Mozilla Firefox ESR affected
Version Status Constraints
unspecified affected
< 115.34
Mozilla Firefox ESR affected
Version Status Constraints
unspecified affected
< 140.9
Mozilla Thunderbird affected
Version Status Constraints
unspecified affected
< 149
Mozilla Thunderbird affected
Version Status Constraints
unspecified affected
< 140.9

Configuration 1 [-]

OR cpe:2.3:a:mozilla:firefox:*:*:*:*:esr:*:*:*
cpe:2.3:a:mozilla:firefox:*:*:*:*:-:*:*:*
cpe:2.3:a:mozilla:firefox:*:*:*:*:esr:*:*:*

No data.

No data.

Subscriptions

Vendors Products
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Firefox Subscribe

Tracking

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Advisories

No advisories yet.

Fixes

Solution

No solution given by the vendor.

Workaround

No workaround given by the vendor.

References
Link Providers
https://bugzilla.mozilla.org/show_bug.cgi?id=2017512 cve-icon cve-icon
https://www.mozilla.org/security/advisories/mfsa2026-20/ cve-icon cve-icon
https://www.mozilla.org/security/advisories/mfsa2026-21/ cve-icon cve-icon
https://www.mozilla.org/security/advisories/mfsa2026-22/ cve-icon cve-icon
https://www.mozilla.org/security/advisories/mfsa2026-23/ cve-icon cve-icon
https://www.mozilla.org/security/advisories/mfsa2026-24/ cve-icon cve-icon
History

Tue, 24 Mar 2026 20:30:00 +0000

Type Values Removed Values Added
Description Use-after-free in the CSS Parsing and Computation component. This vulnerability affects Firefox < 149, Firefox ESR < 115.34, and Firefox ESR < 140.9. Use-after-free in the CSS Parsing and Computation component. This vulnerability affects Firefox < 149, Firefox ESR < 115.34, Firefox ESR < 140.9, Thunderbird < 149, and Thunderbird < 140.9.
References

Tue, 24 Mar 2026 19:30:00 +0000

Type Values Removed Values Added
First Time appeared Mozilla
Mozilla firefox
Weaknesses CWE-416
CPEs cpe:2.3:a:mozilla:firefox:*:*:*:*:-:*:*:*
cpe:2.3:a:mozilla:firefox:*:*:*:*:esr:*:*:*
Vendors & Products Mozilla
Mozilla firefox
Metrics cvssV3_1

{'score': 9.8, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H'}

Tue, 24 Mar 2026 12:45:00 +0000

Type Values Removed Values Added
Description Use-after-free in the CSS Parsing and Computation component. This vulnerability affects Firefox < 149, Firefox ESR < 115.34, and Firefox ESR < 140.9.
Title Use-after-free in the CSS Parsing and Computation component
References
cve-icon MITRE

Status: PUBLISHED

Assigner: mozilla

Published:

Updated: 2026-03-24T20:27:22.137Z

Reserved: 2026-03-23T23:21:44.154Z

Link: CVE-2026-4691

cve-icon Vulnrichment

No data.

cve-icon NVD

Status : Modified

Published: 2026-03-24T13:16:04.937

Modified: 2026-03-24T21:16:30.747

Link: CVE-2026-4691

cve-icon Redhat

No data.

cve-icon OpenCVE Enrichment

No data.

Weaknesses