CVE-2025-6429

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

Severity Score

6.5

*CVSS v3.1

Exploit Likelihood

*EPSS

Affected Versions

*CPE

Public Exploits

*Multiple Sources

Exploited in Wild

*KEV

Decision

Track

*SSVC

Descriptions

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 and Firefox ESR < 128.12.

A flaw was found in Firefox and Thunderbird. The Mozilla Foundation's Security Advisory describes the following issue: 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 update for MozillaFirefox fixes the following issues. Use-after-free in FontFaceSet The WebCompat WebExtension shipped with Firefox exposed a persistent UUID No warning when opening executable terminal files on macOS Incorrect parsing of URLs could have allowed embedding of youtube.com Content-Disposition header ignored when a file is included in an embed or object tag.

*Credits: Masato Kinugawa

CVSS Scores

Attack Vector

Network

Attack Complexity

Low

Privileges Required

None

User Interaction

Required

Scope

Unchanged

Confidentiality

None

Integrity

High

Availability

None

Attack Vector

Network

Attack Complexity

Low

Privileges Required

None

User Interaction

Required

Scope

Changed

Confidentiality

Low

Integrity

Low

Availability

None

Attack Vector

Network

Attack Complexity

Low

Authentication

None

Confidentiality

None

Integrity

Complete

Availability

None

* Common Vulnerability Scoring System

SSVC

Decision:Track

Exploitation

None

Automatable

Tech. Impact

Partial

* Organization's Worst-case Scenario

Timeline

2025-06-20 CVE Reserved
2025-06-24 CVE Published
2025-07-14 CVE Updated
2025-08-18 EPSS Updated
---------- Exploited in Wild
---------- KEV Due Date
---------- First Exploit

CWE

CWE-116: Improper Encoding or Escaping of Output
CWE-706: Use of Incorrectly-Resolved Name or Reference

CAPEC

References (7)

URL	Tag	Source
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

URL	Date	SRC

URL	Date	SRC

URL	Date	SRC
https://access.redhat.com/security/cve/CVE-2025-6429	2025-07-02
https://bugzilla.redhat.com/show_bug.cgi?id=2374561	2025-07-02

Affected Vendors, Products, and Versions

Vendor		Product				Version		Other		Status
Vendor	Product	Version	Other	Status	<-- -->	Vendor	Product	Version	Other	Status
Mozilla Search vendor "Mozilla"		Firefox Search vendor "Mozilla" for product "Firefox"				*		-		Affected
Mozilla Search vendor "Mozilla"		Firefox Esr Search vendor "Mozilla" for product "Firefox Esr"				*		-		Affected
Mozilla Search vendor "Mozilla"		Thunderbird Search vendor "Mozilla" for product "Thunderbird"				*		-		Affected
Oracle Search vendor "Oracle"		Linux Search vendor "Oracle" for product "Linux"				*		-		Affected
Redhat Search vendor "Redhat"		Enterprise Linux Search vendor "Redhat" for product "Enterprise Linux"				*		-		Affected
Redhat Search vendor "Redhat"		Rhel Aus Search vendor "Redhat" for product "Rhel Aus"				*		-		Affected
Redhat Search vendor "Redhat"		Rhel E4s Search vendor "Redhat" for product "Rhel E4s"				*		-		Affected
Redhat Search vendor "Redhat"		Rhel Eus Search vendor "Redhat" for product "Rhel Eus"				*		-		Affected
Redhat Search vendor "Redhat"		Rhel Tus Search vendor "Redhat" for product "Rhel Tus"				*		-		Affected
Alma Search vendor "Alma"		Linux Search vendor "Alma" for product "Linux"				*		-		Affected
Debian Search vendor "Debian"		Debian Linux Search vendor "Debian" for product "Debian Linux"				*		-		Affected
Fedoraproject Search vendor "Fedoraproject"		Fedora Search vendor "Fedoraproject" for product "Fedora"				*		-		Affected
Freebsd Search vendor "Freebsd"		Freebsd Search vendor "Freebsd" for product "Freebsd"				*		-		Affected
Opensuse Search vendor "Opensuse"		Leap Search vendor "Opensuse" for product "Leap"				*		-		Affected
Oracle Search vendor "Oracle"		Linux Search vendor "Oracle" for product "Linux"				*		-		Affected
Redhat Search vendor "Redhat"		Enterprise Linux Search vendor "Redhat" for product "Enterprise Linux"				*		-		Affected
Redhat Search vendor "Redhat"		Rhel Aus Search vendor "Redhat" for product "Rhel Aus"				*		-		Affected
Redhat Search vendor "Redhat"		Rhel E4s Search vendor "Redhat" for product "Rhel E4s"				*		-		Affected
Redhat Search vendor "Redhat"		Rhel Els Search vendor "Redhat" for product "Rhel Els"				*		-		Affected
Redhat Search vendor "Redhat"		Rhel Eus Search vendor "Redhat" for product "Rhel Eus"				*		-		Affected
Redhat Search vendor "Redhat"		Rhel Tus Search vendor "Redhat" for product "Rhel Tus"				*		-		Affected
Slackware Search vendor "Slackware"		Slackware Linux Search vendor "Slackware" for product "Slackware Linux"				*		-		Affected
Suse Search vendor "Suse"		Sle-module-desktop-applications Search vendor "Suse" for product "Sle-module-desktop-applications"				*		-		Affected
Suse Search vendor "Suse"		Sle Hpc-espos Search vendor "Suse" for product "Sle Hpc-espos"				*		-		Affected
Suse Search vendor "Suse"		Sle Hpc-ltss Search vendor "Suse" for product "Sle Hpc-ltss"				*		-		Affected
Suse Search vendor "Suse"		Sle Hpc Search vendor "Suse" for product "Sle Hpc"				*		-		Affected
Suse Search vendor "Suse"		Sled Search vendor "Suse" for product "Sled"				*		-		Affected
Suse Search vendor "Suse"		Sles-ltss-extended-security Search vendor "Suse" for product "Sles-ltss-extended-security"				*		-		Affected
Suse Search vendor "Suse"		Sles-ltss Search vendor "Suse" for product "Sles-ltss"				*		-		Affected
Suse Search vendor "Suse"		Sles Search vendor "Suse" for product "Sles"				*		-		Affected
Suse Search vendor "Suse"		Sles Sap Search vendor "Suse" for product "Sles Sap"				*		-		Affected