CVE-2025-6429

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 affects Firefox < 140, Firefox ESR < 128.12, Thunderbird < 140, and Thunderbird < 128.12.
ProviderTypeBase ScoreAtk. VectorAtk. ComplexityPriv. RequiredVector
NISTNIST
6.5 MEDIUM
NETWORK
LOW
NONE
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:N
mozillaCNA
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CISA-ADPADP
6.5 MEDIUM
NETWORK
LOW
NONE
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:N
CVEADP
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Base Score
CVSS 3.x
EPSS Score
Percentile: 27%
VendorProductVersion
mozillafirefox
𝑥
< 128.12.0
mozillafirefox
𝑥
< 140.0
𝑥
= Vulnerable software versions
Debian logo
Debian Releases
Debian Product
Codename
firefox
sid
144.0.2-1
fixed
firefox-esr
bullseye
vulnerable
bullseye (security)
140.4.0esr-1~deb11u1
fixed
bookworm
128.14.0esr-1~deb12u1
fixed
bookworm (security)
140.4.0esr-1~deb12u1
fixed
trixie
128.14.0esr-1~deb13u1
fixed
trixie (security)
140.4.0esr-1~deb13u1
fixed
forky
140.4.0esr-1
fixed
sid
140.4.0esr-1
fixed
thunderbird
bullseye
vulnerable
bullseye (security)
1:140.4.0esr-1~deb11u1
fixed
bookworm
1:128.14.0esr-1~deb12u1
fixed
bookworm (security)
1:140.4.0esr-1~deb12u1
fixed
trixie
1:128.14.0esr-1~deb13u1
fixed
trixie (security)
1:140.4.0esr-1~deb13u1
fixed
forky
1:140.4.0esr-1
fixed
sid
1:140.4.0esr-1
fixed
Ubuntu logo
Ubuntu Releases
Ubuntu Product
Codename
mozjs52
plucky
dne
oracular
dne
noble
dne
jammy
dne
focal
ignored
bionic
ignored
firefox
plucky
not-affected
oracular
not-affected
noble
not-affected
jammy
not-affected
thunderbird
plucky
not-affected
oracular
not-affected
noble
not-affected
jammy
Fixed 1:128.12.0+build1-0ubuntu0.22.04.1
released
mozjs38
plucky
dne
oracular
dne
noble
dne
jammy
dne
bionic
needs-triage
mozjs68
plucky
dne
oracular
dne
noble
dne
jammy
dne
focal
ignored
mozjs78
plucky
dne
oracular
dne
noble
dne
jammy
ignored
mozjs91
plucky
dne
oracular
dne
noble
dne
jammy
ignored
mozjs102
plucky
dne
oracular
dne
noble
ignored
jammy
ignored
mozjs115
plucky
ignored
oracular
ignored
noble
ignored
jammy
dne
Common Weakness Enumeration
References
https://bugzilla.mozilla.org/show_bug.cgi?id=1970658
https://www.mozilla.org/security/advisories/mfsa2025-51/
https://www.mozilla.org/security/advisories/mfsa2025-53/
https://www.mozilla.org/security/advisories/mfsa2025-54/
https://www.mozilla.org/security/advisories/mfsa2025-55/
https://lists.debian.org/debian-lts-announce/2025/06/msg00029.html
https://lists.debian.org/debian-lts-announce/2025/07/msg00002.html