CVE-2026-0891 — Improper Restriction of Operations within the Bounds of a Memory Buffer in Mozilla Firefox

CWE-119 — Improper Restriction of Operations within the Bounds of a Memory Buffer12 documents9 sources
Severity
8.1HIGHNVD
EPSS
0.0%
top 93.33%
CISA KEV
Not in KEV
Exploit
No known exploits
Affected products
2
Mozilla ThunderbirdMozilla Firefox
Timeline
PublishedJan 13
Latest updateFeb 2

Description

Memory safety bugs present in Firefox ESR 140.6, Thunderbird ESR 140.6, Firefox 146 and Thunderbird 146. Some of these bugs showed evidence of memory corruption and we presume that with enough effort some of these could have been exploited to run arbitrary code. This vulnerability was fixed in Firefox 147, Firefox ESR 140.7, Thunderbird 147, and Thunderbird 140.7.

CVSS vector

CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:HExploitability: 2.2 | Impact: 5.9

Affected Packages3 packages

▶NVDmozilla/firefox< 140.7.0+1
▶NVDmozilla/thunderbird< 140.7.0+1
▶Debianmozilla/thunderbird< 1:140.7.0esr-1~deb11u1+3

🔴Vulnerability Details

3
OSV
CVE-2026-0891: Memory safety bugs present in Firefox ESR 140↗2026-01-13
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GHSA
GHSA-w588-qjhp-fm98: Memory safety bugs present in Firefox ESR 140↗2026-01-13
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CVEList
Memory safety bugs fixed in Firefox ESR 140.7, Thunderbird ESR 140.7, Firefox 147 and Thunderbird 147↗2026-01-13
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📋Vendor Advisories

7
Ubuntu
Thunderbird vulnerabilities↗2026-02-02
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Red Hat
firefox: thunderbird: Memory safety bugs fixed in Firefox ESR 140.7, Thunderbird ESR 140.7, Firefox 147 and Thunderbird 147↗2026-01-13
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Debian
CVE-2026-0891: firefox - Memory safety bugs present in Firefox ESR 140.6, Thunderbird ESR 140.6, Firefox ...↗2026
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Mozilla
Mozilla Foundation Security Advisory 2026-05: CVE-2026-0891↗
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Mozilla
Mozilla Foundation Security Advisory 2026-03: CVE-2026-0891↗
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🕵️Threat Intelligence

1
Wiz
CVE-2026-0891 Impact, Exploitability, and Mitigation Steps | Wiz↗
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CVE-2026-0891 — Mozilla Firefox vulnerability | cvebase