PT-2026-41913 · Mozilla+1 · Firefox+2

Ameen Basha M K · CVE-2026-8959 · Published 2026-05-19 · Updated 2026-06-29

Positive Technologies (AI Summary)

CVSS v3.1

9.6

Critical

Base vector

AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:H

Name of the Vulnerable Software and Affected Versions Firefox versions prior to 151 Firefox ESR versions prior to 140.11 Thunderbird versions prior to 151 Thunderbird versions prior to 140.11

Description Incorrect boundary conditions in the Widget: Win32 component allow for a sandbox escape, which occurs when a process breaks out of its restricted environment to access the broader system.

Recommendations Update to version 151 Update to version 140.11 Update to version 151 Update to version 140.11

Fix

DoS

Protection Mechanism Failure

RCE

Buffer Overflow

Weakness Enumeration

CWE-693

CWE-20

CWE-119

Related Identifiers

ALSA-2026:21381

ALSA-2026:22325

ALSA-2026:22643

CVE-2026-8959

OESA-2026-2392

OESA-2026-2393

OESA-2026-2394

OESA-2026-2465

OPENSUSE-SU-2026:10813-1

OPENSUSE-SU-2026:10863-1

OPENSUSE-SU-2026:10864-1

OPENSUSE-SU-2026:21168-1

RHSA-2026:26174

RHSA-2026:26268

RHSA-2026:26269

RHSA-2026:26270

RHSA-2026:26521

RHSA-2026:26536

RHSA-2026:26539

Affected Products

Firefox

Rocky Linux

Thunderbird

References · 181

• https://nvd.nist.gov/vuln/detail/CVE-2026-8947 · Security Note
• https://nvd.nist.gov/vuln/detail/CVE-2026-8388 · Security Note
• https://errata.almalinux.org/10/ALSA-2026-22325.html · Vendor Advisory
• https://linux.oracle.com/errata/ELSA-2026-21381.html · Vendor Advisory
• https://nvd.nist.gov/vuln/detail/CVE-2026-8391 · Security Note
• https://mozilla.org/security/advisories/mfsa2026-51/#CVE-2026-8959 · Vendor Advisory
• https://osv.dev/vulnerability/OESA-2026-2465 · Vendor Advisory
• https://cve.org/CVERecord?id=CVE-2026-8959 · Security Note
• https://osv.dev/vulnerability/ALSA-2026:22643 · Vendor Advisory
• https://mozilla.org/en-US/security/advisories/mfsa2026-46/#CVE-2026-8959 · Vendor Advisory
• https://errata.rockylinux.org/RLSA-2026:22643 · Vendor Advisory
• http://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2026-8959 · Security Note
• https://nvd.nist.gov/vuln/detail/CVE-2026-8968 · Security Note
• https://osv.dev/vulnerability/UBUNTU-CVE-2026-8959 · Vendor Advisory
• https://osv.dev/vulnerability/ALSA-2026:21381 · Vendor Advisory