#VU111888 Input validation error in Mozilla products - CVE-2025-6429

Vulnerability identifier: #VU111888

Vulnerability risk: Low

CVSSv4.0: 0.5 [CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:A/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N/E:U/U:Clear]

CVE-ID: CVE-2025-6429

CWE-ID: CWE-20

Exploitation vector: Network

Exploit availability: No

Vulnerable software:
Firefox ESR
Client/Desktop applications / Web browsers
Mozilla Firefox
Client/Desktop applications / Web browsers
Firefox for Android
Mobile applications / Apps for mobile phones

Vendor: Mozilla

Description

The vulnerability allows a remote attacker to bypass implemented security restrictions.

The vulnerability exists due to incorrect parsing of embedded URLs that led to URLs being rewritten to the youtube.com domain. A remote attacker can use a specially crafted embed tag to bypass website security checks that restricted which domains users were allowed to embed.

Mitigation
Install updates from vendor's website.

Vulnerable software versions

Firefox ESR: 128.0, 128.1.0, 128.2.0, 128.3.0, 128.3.1, 128.4.0, 128.5.0, 128.5.1, 128.5.2, 128.6.0, 128.7.0, 128.8.0, 128.8.1, 128.9.0, 128.10.0, 128.10.1, 128.11.0

Mozilla Firefox: 128.0 - 139.0.4

Firefox for Android: 120.0 - 139.0.3

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External links
https://www.mozilla.org/en-US/security/advisories/mfsa2025-53/
https://bugzilla.mozilla.org/show_bug.cgi?id=1970658
https://www.mozilla.org/en-US/security/advisories/mfsa2025-51/

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Q & A

Can this vulnerability be exploited remotely?

Yes. This vulnerability can be exploited by a remote non-authenticated attacker via the Internet.

Is there known malware, which exploits this vulnerability?

No. We are not aware of malware exploiting this vulnerability.