CVE-2026-0891 | Memory safety bugs fixed in Firefox ESR 140.7, Thunderbird ESR 140.7, Firefox 147 and Thunderbird 147

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.

Published: 2026-01-13 Last update: 2026-04-13 Assigner: [email protected] Source: [email protected]
NVD Status：Modified，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2026-0891 is rated Low Risk (34.5/100): CVSS High severity, with low exploitation likelihood (EPSS 0.02%). Monitor for updates and reassess as exploit intelligence or EPSS changes.

Risk is dynamic; we continuously reassess and refresh what is shown on this page as upstream context changes.

Exploit prediction scoring system (EPSS) score for CVE-2026-0891

EPSS lead: Daily EPSS estimates relative likelihood of exploitation; percentile ranks this CVE among scored vulnerabilities (higher = more severe relative rank).

# Date Old EPSS score New EPSS score Delta (New - Old)
1 2026-02-18 0.06% 0.02% -0.04%
2 2026-01-19 0.04% 0.06% +0.02%
3 2026-01-14 — 0.04% —

Full EPSS history (3 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2026-0891

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
8.1 3.1 HIGH
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:H)
Even with access, the exploit needs extra luck, timing, or a fussy environment to actually work.
Privileges required (PR:N)
No account or special rights needed—anonymous or random user is enough.
User interaction (UI:N)
Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:H)
Serious risk that confidential data gets exposed in a big way.
Integrity (I:H)
They could widely tamper with or forge data—trust in the data is badly hurt.
Availability (A:H)
Could take the service down hard or make it unusable for people who depend on it.
 2.2 5.9 134c704f-9b21-4f2e-91b3-4a467353bcc0

Weakness enumeration for CVE-2026-0891

OS Trackers for CVE-2026-0891

vendor priority summary link
alpine — CVE-2026-0891: 3 source package rows (firefox, firefox-esr, thunderbird); 274 state rows across 2 repos (3.23-community, edge-community); fixed 0, open 274. https://security.alpinelinux.org/vuln/CVE-2026-0891
debian not yet assigned CVE-2026-0891 not yet assigned priority: Debian including 3 source packages (firefox, firefox-esr, thunderbird), 11 status rows across 5 suites (bookworm, bullseye, forky, sid, trixie): resolved 11. https://security-tracker.debian.org/tracker/CVE-2026-0891
redhat high — https://access.redhat.com/security/cve/CVE-2026-0891
suse high CVE-2026-0891 severity important: SUSE including 47 source package names (2.2.0-4.49:libopenssl3-3.1.4-slfo.1.1_5.1, 2.2.0-4.50:libopenssl3-3.1.4-slfo.1.1_5.1, …), 215 product×package rows across 87 product lines (Container suse/sl-micro/6.0/baremetal-os-container, Container suse/sl-micro/6.0/base-os-container, … (87 product lines)): Fixed 211, First Fixed 4. https://www.suse.com/security/cve/CVE-2026-0891/
ubuntu medium CVE-2026-0891 medium priority: Ubuntu including 9 source packages (firefox, mozjs102, …), 58 status rows across 8 suites (bionic, focal, jammy, noble, plucky, questing, resolute, upstream): DNE 29, needs-triage 10, ignored 9, not-affected 9, released 1. https://ubuntu.com/security/CVE-2026-0891

Affected software / configurations for CVE-2026-0891

Vendor Product Version Raw CPE
mozilla firefox < 140.7.0 cpe:2.3:a:mozilla:firefox:*:*:*:*:esr:*:*:*
mozilla firefox < 147.0 cpe:2.3:a:mozilla:firefox:*:*:*:*:-:*:*:*
mozilla thunderbird < 140.7.0 cpe:2.3:a:mozilla:thunderbird:*:*:*:*:esr:*:*:*
mozilla thunderbird < 147.0 cpe:2.3:a:mozilla:thunderbird:*:*:*:*:-:*:*:*

References for CVE-2026-0891

cvelogic Threat Intelligence