PT-2026-27390 · Mozilla+1 · Thunderbird+3

Fabius Artrel · Published 2026-01-01 · Updated 2026-04-17 · CVE-2026-4691

Positive Technologies (AI Summary)

CVSS v2.0

10

Critical

Base vector

AV:N/AC:L/Au:N/C:C/I:C/A:C

Name of the Vulnerable Software and Affected Versions Firefox versions prior to 149 Firefox ESR versions prior to 115.34 Firefox ESR versions prior to 140.9 Thunderbird versions prior to 149 Thunderbird versions prior to 140.9

Description A use-after-free issue exists in the CSS Parsing and Computation component. This can potentially allow for unexpected behavior or crashes.

Recommendations Update Firefox to version 149 or later. Update Firefox ESR to version 115.34 or later. Update Firefox ESR to version 140.9 or later. Update Thunderbird to version 149 or later. Update Thunderbird to version 140.9 or later.

Fix

Use After Free

Weakness Enumeration

CWE-416

Related Identifiers

ALSA-2026:5930

ALSA-2026:5931

ALSA-2026:5932

ALSA-2026:6188

ALSA-2026:6342

ALSA-2026:6917

BDU:2026-04815

CVE-2026-4691

MGASA-2026-0080

MGASA-2026-0081

OESA-2026-1705

OESA-2026-1706

OESA-2026-1707

OESA-2026-1708

OESA-2026-1709

OESA-2026-1993

OESA-2026-1994

OPENSUSE-SU-2026:10413-1

OPENSUSE-SU-2026:10447-1

OPENSUSE-SU-2026:10458-1

OPENSUSE-SU-2026:20439-1

RHSA-2026:5930

RHSA-2026:5931

RHSA-2026:5932

RHSA-2026:6188

RHSA-2026:6342

RHSA-2026:6917

RHSA-2026:7837

RHSA-2026:7838

RHSA-2026:7839

RHSA-2026:7840

RHSA-2026:7841

RHSA-2026:7842

RHSA-2026:7843

RHSA-2026:7845

RHSA-2026:7858

RHSA-2026:8284

RHSA-2026:8285

RHSA-2026:8286

RHSA-2026:8287

RHSA-2026:8288

RHSA-2026:8289

RHSA-2026:8290

RHSA-2026:8315

RHSA-2026:8427

RHSA-2026:8850

SUSE-SU-2026:1126-1

SUSE-SU-2026:1127-1

SUSE-SU-2026:1163-1

SUSE-SU-2026:20978-1

Affected Products

Firefox

Firefox Esr

Rocky Linux

Thunderbird

References · 256

• https://nvd.nist.gov/vuln/detail/CVE-2026-4702 · Security Note
• https://nvd.nist.gov/vuln/detail/CVE-2025-59375 · Security Note
• https://nvd.nist.gov/vuln/detail/CVE-2026-4686 · Security Note
• https://osv.dev/vulnerability/openSUSE-SU-2026:10447-1 · Vendor Advisory
• https://advisories.mageia.org/MGASA-2026-0081.html · Security Note
• https://linux.oracle.com/errata/ELSA-2026-5932.html · Vendor Advisory
• https://nvd.nist.gov/vuln/detail/CVE-2026-4693 · Security Note
• https://mozilla.org/en-US/security/advisories/mfsa2026-22 · Vendor Advisory
• https://osv.dev/vulnerability/OESA-2026-1708 · Vendor Advisory
• https://nvd.nist.gov/vuln/detail/CVE-2026-4690 · Security Note
• https://nvd.nist.gov/vuln/detail/CVE-2026-4371 · Security Note
• https://osv.dev/vulnerability/openSUSE-SU-2026:20439-1 · Vendor Advisory
• https://nvd.nist.gov/vuln/detail/CVE-2026-4698 · Security Note
• https://osv.dev/vulnerability/SUSE-SU-2026:1127-1 · Vendor Advisory
• https://mozilla.org/security/advisories/mfsa2026-20 · Vendor Advisory