medium 6.5

CVE-2025-6429 json

Incorrect parsing of URLs could have allowed embedding of youtube.com

published 2025-06-24 16 mo ago modified 2026-09-30 39 d ago also EUVD-2025-21378

cvss: 6.5; version 3.1, CNA
cisa kev: Not listed; not in CISA's catalog
epss: 0.4%; EPSS 0.4% chance of exploitation in 30 days, percentile 29%
public exploits: 0; none known

Firefox could have incorrectly parsed a URL and rewritten it to the youtube.com domain when parsing the URL specified in an `embed` tag. This could have bypassed website security checks that restricted which domains users were allowed to embed. This vulnerability was fixed in Firefox 140, Firefox ESR 128.12, Thunderbird 140, and Thunderbird 128.12.

Patch / fix

fixed in 2 distros 7

mozilla firefox 128.12, 140
mozilla firefox_esr 128.12, 140

debian ubuntu red hat suse opensuse almalinux rocky linux

firefox-esr Debian 12 128.12.0esr-1~deb12u1
firefox-esr Debian 14, Debian 13 128.12.0esr-1
thunderbird Debian 12 1:128.12.0esr-1~deb12u1
thunderbird Debian 14, Debian 13 1:128.12.0esr-1

debian advisories DEBIAN-CVE-2025-6429

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

ubuntu advisories UBUNTU-CVE-2025-6429

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 8 128.12.0-1.el8_10
thunderbird RHEL 9 128.12.0-1.el9_6
thunderbird RHEL 10.0 128.12.0-1.el10_0
firefox RHEL 8 128.12.0-1.el8_10
firefox RHEL 10.0 128.12.0-1.el10_0
firefox RHEL 9 128.12.0-1.el9_6
firefox-x11 RHEL 9 128.12.0-1.el9_6
firefox RHEL 9.4 EUS 128.12.0-1.el9_4

red hat advisories RHSA-2025:10246 RHSA-2025:10196 RHSA-2025:10195 RHSA-2025:10188 RHSA-2025:10186 RHSA-2025:10187

mozjs128 SLES for SAP applications 16.0, SLES 16.0 128.14.0-160000.1.1
MozillaThunderbird SLE Workstation Extension 15 SP7, SLE Workstation Extension 15 SP6, SLE Module for Package Hub 15 SP7 +2 more 140.1.0-150200.8.230.1
MozillaFirefox-branding-SLE SLES for SAP 15 SP5, SLES for SAP 15 SP4, SLES for SAP 15 SP3 +12 more 140-150200.9.21.1
pipewire SLE Module for Package Hub 15 SP7, SLE Module for Package Hub 15 SP6 0.3.6-150200.3.11.1
pipewire SLES for SAP 15 SP3, SLES 15 SP3-LTSS, SLE High Performance Computing 15 SP3-LTSS +1 more 0.3.24-150300.4.8.1
pipewire SLES for SAP 15 SP4, SLES 15 SP4-LTSS, SLE High Performance Computing 15 SP4-LTSS +1 more 0.3.49-150400.3.7.1
pipewire SLES for SAP 15 SP5, SLES 15 SP5-LTSS, SLE High Performance Computing 15 SP5-LTSS +1 more 0.3.64-150500.3.7.2
MozillaFirefox SLES for SAP 15 SP5, SLES for SAP 15 SP4, SLES for SAP 15 SP3 +12 more 140.1.0-150200.152.193.1

suse advisories SUSE-SU-2025:21170-1 SUSE-SU-2025:02546-1 SUSE-SU-2025:02529-1 SUSE-SU-2025:02368-1 SUSE-SU-2025:02339-1 SUSE-SU-2025:02123-1

mozjs128 openSUSE Leap 16.0 128.14.0-160000.1.1
MozillaFirefox openSUSE Tumbleweed 140.0.2-1.1
MozillaThunderbird openSUSE Tumbleweed 128.12.0-1.1
mozjs128 openSUSE Tumbleweed 128.12.0-1.1
firefox-esr openSUSE Tumbleweed 128.12.0-1.1

opensuse advisories openSUSE-SU-2025:20135-1 openSUSE-SU-2025:15325-1 openSUSE-SU-2025:15312-1 openSUSE-SU-2025:15315-1 openSUSE-SU-2025:15216-1

thunderbird AlmaLinux 8 128.12.0-1.el8_10.alma.1
firefox AlmaLinux 9 128.12.0-1.el9_6.alma.1
firefox-x11 AlmaLinux 9 128.12.0-1.el9_6.alma.1
firefox AlmaLinux 10 128.12.0-1.el10_0
firefox AlmaLinux 8 128.12.0-1.el8_10.alma.1

almalinux advisories ALSA-2025:10246 ALSA-2025:10072 ALSA-2025:10073 ALSA-2025:10074

firefox Rocky Linux 9 128.12.0-1.el9_6
thunderbird Rocky Linux 9 128.12.0-1.el9_6
firefox Rocky Linux 10 128.12.0-1.el10_0
thunderbird Rocky Linux 10 128.12.0-1.el10_0
firefox Rocky Linux 8 128.12.0-1.el8_10
thunderbird Rocky Linux 8 128.12.0-1.el8_10

rocky linux advisories RLSA-2025:10072 RLSA-2025:10196 RLSA-2025:10073 RLSA-2025:10195 RLSA-2025:10074 RLSA-2025:10246

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-2025-6429 updated 2026-11-05 cvss 6.1

firefox: thunderbird: Incorrect parsing of URLs could have allowed embedding of youtube.com

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 10 firefox-flatpak, thunderbird-flatpak
affected: no fix available
Red Hat Enterprise Linux AppStream (v. 8) firefox 128.12.0-1.el8_10, thunderbird 128.12.0-1.el8_10
fixed: vendor fix RHSA-2025:10074
Red Hat Enterprise Linux AppStream (v. 9) firefox 128.12.0-1.el9_6, firefox-x11 128.12.0-1.el9_6, thunderbird 128.12.0-1.el9_6
fixed: vendor fix RHSA-2025:10072
Red Hat Enterprise Linux AppStream (v. 10) firefox 128.12.0-1.el10_0, thunderbird 128.12.0-1.el10_0
fixed: vendor fix RHSA-2025:10073
Red Hat Enterprise Linux AppStream AUS (v. 8.2) firefox 128.12.0-1.el8_2, thunderbird 128.12.0-1.el8_2
fixed: vendor fix RHSA-2025:10182
Red Hat Enterprise Linux AppStream AUS (v.8.4) firefox 128.12.0-1.el8_4, thunderbird 128.12.0-1.el8_4
fixed: vendor fix RHSA-2025:10184
Red Hat Enterprise Linux AppStream AUS (v.8.6) firefox 128.12.0-1.el8_6, thunderbird 128.12.0-1.el8_6 Red Hat Enterprise Linux AppStream E4S (v.8.6) firefox 128.12.0-1.el8_6, thunderbird 128.12.0-1.el8_6
fixed: vendor fix RHSA-2025:10183

show 7 more

Red Hat Enterprise Linux AppStream E4S (v.8.8) firefox 128.12.0-1.el8_8, thunderbird 128.12.0-1.el8_8
fixed: vendor fix RHSA-2025:10186
Red Hat Enterprise Linux AppStream E4S (v.9.0) firefox 128.12.0-1.el9_0, thunderbird 128.12.0-1.el9_0
fixed: vendor fix RHSA-2025:10187
Red Hat Enterprise Linux AppStream E4S (v.9.2) firefox 128.12.0-1.el9_2, firefox-x11 128.12.0-1.el9_2, thunderbird 128.12.0-1.el9_2
fixed: vendor fix RHSA-2025:10185
Red Hat Enterprise Linux AppStream EUS (v.9.4) firefox 128.12.0-1.el9_4, firefox-x11 128.12.0-1.el9_4, thunderbird 128.12.0-1.el9_4
fixed: vendor fix RHSA-2025:10188
Red Hat Enterprise Linux AppStream TUS (v.8.6) firefox 128.12.0-1.el8_6, thunderbird 128.12.0-1.el8_6
fixed: vendor fix RHSA-2025:10183
Red Hat Enterprise Linux AppStream TUS (v.8.8) firefox 128.12.0-1.el8_8, thunderbird 128.12.0-1.el8_8
fixed: vendor fix RHSA-2025:10186
Red Hat Enterprise Linux Server (v. 7 ELS) firefox 128.12.0-1.el7_9
fixed: vendor fix RHSA-2025:10181

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: 16 mo ago (2025-06-25)

Exploit prediction

0.36% chance of exploitation in the next 30 days, higher than 29% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by	version	score	vector
CISA ADP	3.1	6.5	CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:N
CNA	3.1	6.5	CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:N

Affected products

Mozilla Firefox
Mozilla Thunderbird

Classification

Weakness

CWE-116 Improper Encoding or Escaping of Output

References

mozilla.org /security/advisories/mfsa2025-51/
vendor-advisory
mozilla.org /security/advisories/mfsa2025-53/
vendor-advisory
bugzilla.mozilla.org /show_bug.cgi?id=1970658
permissions-required
mozilla.org /security/advisories/mfsa2025-54/
mozilla.org /security/advisories/mfsa2025-55/
lists.debian.org /debian-lts-announce/2025/07/msg00002.html
lists.debian.org /debian-lts-announce/2025/06/msg00029.html

Sources

CVE List CVE-2025-6429
NVD CVE-2025-6429

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