medium 4.8

CVE-2025-4087 json

Unsafe attribute access during XPath parsing

published 2025-04-29 last yr. modified 2026-10-05 last mo. also EUVD-2025-12657

cvss: 4.8; version 3.1, CNA
cisa kev: Not listed; not in CISA's catalog
epss: 0.3%; EPSS 0.3% chance of exploitation in 30 days, percentile 25%
public exploits: 0; none known

A vulnerability was identified in Thunderbird where XPath parsing could trigger undefined behavior due to missing null checks during attribute access. This could lead to out-of-bounds read access and potentially, memory corruption. This vulnerability was fixed in Firefox 138, Firefox ESR 128.10, Thunderbird 138, and Thunderbird 128.10.

Patch / fix

fixed in 4 distros 7

mozilla firefox 128.10, 138
mozilla firefox_esr 128.10, 138
mozilla thunderbird 128.10, 138
mozilla thunderbird_esr 128.10, 138

debian ubuntu red hat suse opensuse almalinux rocky linux

firefox-esr Debian 12 128.10.0esr-1~deb12u1
firefox-esr Debian 14, Debian 13 128.10.0esr-1
thunderbird Debian 12 1:128.10.0esr-1~deb12u1
thunderbird Debian 14, Debian 13 1:128.10.0esr-1

debian advisories DEBIAN-CVE-2025-4087

thunderbird Ubuntu 22.04 LTS 1:128.12.0+build1-0ubuntu0.22.04.1

ubuntu advisories UBUNTU-CVE-2025-4087

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

thunderbird RHEL 10.0 128.10.0-1.el10_0
firefox RHEL 10.0 128.10.0-1.el10_0
firefox RHEL 9 128.10.0-1.el9_6
firefox-x11 RHEL 9 128.10.0-1.el9_6
thunderbird RHEL 8 128.10.0-1.el8_10
thunderbird RHEL 9 128.10.0-1.el9_5
firefox RHEL 8 128.10.0-1.el8_10
firefox RHEL 9 128.10.0-1.el9_5

red hat advisories RHSA-2025:7695 RHSA-2025:7694 RHSA-2025:7693 RHSA-2025:7691 RHSA-2025:7692 RHSA-2025:7690

MozillaThunderbird SLE Workstation Extension 15 SP6, SLE Module for Package Hub 15 SP6, openSUSE Leap 15.6 128.10.0-150200.8.212.1
MozillaFirefox SLES for SAP 15 SP5, SLES for SAP 15 SP4, SLES for SAP 15 SP3 +11 more 128.10.0-150200.152.179.1

suse advisories SUSE-SU-2025:1506-1 SUSE-SU-2025:1436-1

firefox-esr openSUSE Tumbleweed 153.0-1.1
MozillaFirefox openSUSE Tumbleweed 138.0-1.1
MozillaThunderbird openSUSE Tumbleweed 128.10.0-1.1

opensuse advisories openSUSE-SU-2026:11373-1 openSUSE-SU-2025:15045-1 openSUSE-SU-2025:15042-1

firefox AlmaLinux 9 128.10.0-1.el9_6.alma.1
firefox-x11 AlmaLinux 9 128.10.0-1.el9_6.alma.1
firefox AlmaLinux 10 128.10.0-1.el10_0
thunderbird AlmaLinux 10 128.10.0-1.el10_0.alma.1
thunderbird AlmaLinux 8 128.10.0-1.el8_10.alma.1
firefox AlmaLinux 9 128.10.0-1.el9_5.alma.1
firefox-x11 AlmaLinux 9 128.10.0-1.el9_5.alma.1
firefox AlmaLinux 8 128.10.0-1.el8_10.alma.1

almalinux advisories ALSA-2025:7428 ALSA-2025:7506 ALSA-2025:7507 ALSA-2025:4797 ALSA-2025:4443 ALSA-2025:4458

firefox Rocky Linux 9 128.10.0-1.el9_5
thunderbird Rocky Linux 9 128.10.0-1.el9_5
firefox Rocky Linux 8 128.10.0-1.el8_10
thunderbird Rocky Linux 8 128.10.0-1.el8_10

rocky linux advisories RLSA-2025:4443 RLSA-2025:4460 RLSA-2025:7428 RLSA-2025:4458 RLSA-2025:4797

Is CVE-2025-4087 in your stack? Fencer shows which of your repositories are affected as soon as an advisory lands, and opens the fix as a pull request.

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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-2025-4087 updated 2026-11-05 cvss 7.6

firefox: thunderbird: Unsafe attribute access during XPath parsing

Red Hat Enterprise Linux 6 firefox, thunderbird Red Hat Enterprise Linux 7 thunderbird
affected: no fix planned “Out of support scope”
Red Hat Enterprise Linux 9 firefox-flatpak-container, thunderbird-flatpak-container Red Hat Enterprise Linux 10 firefox-flatpak-container, thunderbird-flatpak-container
affected: no fix available
Red Hat Enterprise Linux AppStream (v. 8) firefox 128.10.0-1.el8_10, thunderbird 128.10.0-1.el8_10
fixed: vendor fix RHSA-2025:4458
Red Hat Enterprise Linux AppStream (v. 9) firefox 128.10.0-1.el9_5, firefox 128.10.0-1.el9_6, firefox-x11 128.10.0-1.el9_5, firefox-x11 128.10.0-1.el9_6, thunderbird 128.10.0-1.el9_5
fixed: vendor fix RHSA-2025:4443
Red Hat Enterprise Linux AppStream (v. 10) firefox 128.10.0-1.el10_0, thunderbird 128.10.0-1.el10_0
fixed: vendor fix RHSA-2025:7506
Red Hat Enterprise Linux AppStream AUS (v. 8.2) firefox 128.10.0-1.el8_2, thunderbird 128.10.0-1.el8_2
fixed: vendor fix RHSA-2025:7547
Red Hat Enterprise Linux AppStream AUS (v.8.4) firefox 128.10.0-1.el8_4, thunderbird 128.10.0-1.el8_4
fixed: vendor fix RHSA-2025:7545
Red Hat Enterprise Linux AppStream AUS (v.8.6) firefox 128.10.0-1.el8_6, thunderbird 128.10.0-1.el8_6
fixed: vendor fix RHSA-2025:7544

show 9 more

Red Hat Enterprise Linux AppStream E4S (v.8.4) firefox 128.10.0-1.el8_4, thunderbird 128.10.0-1.el8_4
fixed: vendor fix RHSA-2025:7545
Red Hat Enterprise Linux AppStream E4S (v.8.6) firefox 128.10.0-1.el8_6, thunderbird 128.10.0-1.el8_6
fixed: vendor fix RHSA-2025:7544
Red Hat Enterprise Linux AppStream E4S (v.9.0) firefox 128.10.0-1.el9_0, thunderbird 128.10.0-1.el9_0
fixed: vendor fix RHSA-2025:4753
Red Hat Enterprise Linux AppStream EUS (v.8.8) firefox 128.10.0-1.el8_8, thunderbird 128.10.0-1.el8_8
fixed: vendor fix RHSA-2025:7543
Red Hat Enterprise Linux AppStream EUS (v.9.2) firefox 128.10.0-1.el9_2, firefox-x11 128.10.0-1.el9_2, thunderbird 128.10.0-1.el9_2
fixed: vendor fix RHSA-2025:4752
Red Hat Enterprise Linux AppStream EUS (v.9.4) firefox 128.10.0-1.el9_4, firefox-x11 128.10.0-1.el9_4, thunderbird 128.10.0-1.el9_4
fixed: vendor fix RHSA-2025:4756
Red Hat Enterprise Linux AppStream TUS (v.8.4) firefox 128.10.0-1.el8_4, thunderbird 128.10.0-1.el8_4
fixed: vendor fix RHSA-2025:7545
Red Hat Enterprise Linux AppStream TUS (v.8.6) firefox 128.10.0-1.el8_6, thunderbird 128.10.0-1.el8_6
fixed: vendor fix RHSA-2025:7544
Red Hat Enterprise Linux Server (v. 7 ELS) firefox 128.10.0-1.el7_9
fixed: vendor fix RHSA-2025:4751

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: no
Technical impact: partial
Assessed: last yr. (2025-04-29)

Exploit prediction

0.32% chance of exploitation in the next 30 days, higher than 25% of all scored CVEs (FIRST EPSS, 2026-11-09).

CVSS scores

assigned by	version	score	vector
CISA ADP	3.1	4.8	CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:N
CNA	3.1	4.8	CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:N

Affected products

Mozilla Firefox
Mozilla Thunderbird

Classification

Weakness

CWE-125 Out-of-bounds Read

References

mozilla.org /security/advisories/mfsa2025-28/
vendor-advisory
mozilla.org /security/advisories/mfsa2025-29/
vendor-advisory
mozilla.org /security/advisories/mfsa2025-31/
vendor-advisory
mozilla.org /security/advisories/mfsa2025-32/
vendor-advisory
bugzilla.mozilla.org /show_bug.cgi?id=1952465
permissions-required
lists.debian.org /debian-lts-announce/2025/05/msg00024.html

Sources

CVE List CVE-2025-4087
NVD CVE-2025-4087

Fencer Intel 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.

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