Memory safety bugs fixed in Firefox 142 and Thunderbird 142

published 2025-08-19 14 mo ago modified 2026-09-30 39 d ago also EUVD-2025-25239

cvss: 9.8; 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 42%
public exploits: 0; none known

Memory safety bugs present in Firefox 141 and Thunderbird 141. 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 142 and Thunderbird 142.

Patch / fix

fixed in 4 distros 2

mozilla firefox 142
mozilla firefox_esr 142
mozilla thunderbird 142
mozilla thunderbird_esr 142

suse opensuse

mozilla-nss SLES for SAP 15 SP5, SLES for SAP 15 SP4, SLES 15 SP5-LTSS +13 more 3.112.2-150400.3.60.1
mozilla-nss SLES for SAP 15 SP3, SLES 15 SP3-LTSS, SLE Micro 5.2 +3 more 3.112.2-150000.3.132.1
MozillaFirefox SLES for SAP 15 SP5, SLES for SAP 15 SP4, SLES for SAP 15 SP3 +12 more 140.2.0-150200.152.198.1
mozilla-nss SLES LTSS Extended Security 12 SP5, SLES 12 SP5-LTSS 3.112.2-58.133.1
MozillaFirefox SLES LTSS Extended Security 12 SP5, SLES 12 SP5-LTSS 140.2.0-112.276.1

suse advisories SUSE-SU-2025:3804-1 SUSE-SU-2025:3760-1 SUSE-SU-2025:3759-1 SUSE-SU-2025:03009-1 SUSE-SU-2025:03008-1

firefox-esr openSUSE Tumbleweed 153.0-1.1
MozillaFirefox openSUSE Tumbleweed 142.0.1-1.1

opensuse advisories openSUSE-SU-2026:11373-1 openSUSE-SU-2025:15516-1

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2025-9187 updated 2026-11-04 cvss 7.5

firefox: thunderbird: Memory safety bugs fixed in Firefox 142 and Thunderbird 142

Red Hat Enterprise Linux 6 firefox, thunderbird Red Hat Enterprise Linux 7 firefox, thunderbird Red Hat Enterprise Linux 8 firefox, thunderbird Red Hat Enterprise Linux 9 firefox, firefox-x11, thunderbird Red Hat Enterprise Linux 10 firefox, thunderbird, firefox-flatpak, thunderbird-flatpak
not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

CISA SSVC

Exploitation: none
Automatable: yes
Technical impact: total
Assessed: 14 mo ago (2025-08-21)

Exploit prediction

0.49% chance of exploitation in the next 30 days, higher than 42% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by	version	score	vector
CISA ADP	3.1	9.8	CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
NVD	3.1	9.8	CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
CNA	3.1	9.8	CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Affected products

Mozilla Firefox
Mozilla Thunderbird

Classification

Weakness

CWE-119 Improper Restriction of Operations within the Bounds of a Memory Buffer

References

mozilla.org /security/advisories/mfsa2025-64/
vendor-advisory
mozilla.org /security/advisories/mfsa2025-70/
vendor-advisory
bugzilla.mozilla.org /buglist.cgi?bug_id=1825621%2C1970079%2C1976736%2C1979072
broken-link

Sources

CVE List CVE-2025-9187
NVD CVE-2025-9187

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