Memory safety bugs fixed in Firefox 137 and Thunderbird 137

published 2025-04-01 19 mo ago modified 2026-09-30 39 d ago also EUVD-2025-9304

cvss: 8.1; version 3.1, CNA
cisa kev: Not listed; not in CISA's catalog
epss: 0.5%; EPSS 0.5% chance of exploitation in 30 days, percentile 41%
public exploits: 0; none known

Memory safety bugs present in Firefox 136 and Thunderbird 136. 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 137 and Thunderbird 137.

Patch / fix

fixed in 4 distros 2

mozilla firefox 137
mozilla firefox_esr 137
mozilla thunderbird 137
mozilla thunderbird_esr 137

ubuntu opensuse

thunderbird Ubuntu 22.04 LTS 1:140.7.1+build1-0ubuntu0.22.04.1

ubuntu advisories UBUNTU-CVE-2025-3034

Ubuntu security data © Canonical Ltd., from https://github.com/canonical/ubuntu-security-notices via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

firefox-esr openSUSE Tumbleweed 153.0-1.1
MozillaFirefox openSUSE Tumbleweed 137.0-1.1

opensuse advisories openSUSE-SU-2026:11373-1 openSUSE-SU-2025:14971-1

CISA SSVC

Exploitation: none
Automatable: no
Technical impact: total
Assessed: 19 mo ago (2025-04-02)

Exploit prediction

0.48% chance of exploitation in the next 30 days, higher than 41% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by	version	score	vector
CISA ADP	3.1	8.1	CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H
CNA	3.1	8.1	CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H

Affected products

Mozilla Firefox
Mozilla Thunderbird

Classification

Weakness

CWE-787 Out-of-bounds Write

References

mozilla.org /security/advisories/mfsa2025-20/
vendor-advisory
mozilla.org /security/advisories/mfsa2025-23/
vendor-advisory
bugzilla.mozilla.org /buglist.cgi?bug_id=1894100%2C1934086%2C1950360
broken-link, issue-tracking

Sources

CVE List CVE-2025-3034
NVD CVE-2025-3034

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.

CPEs and fixed versions use Anchore's correction of NVD's data: Added CPE configurations because not yet analyzed by NVD.

Summary