CVE-2025-6430

MEDIUM

Firefox < 140.0 and 128.12-128.* - Cross-Site Scripting via Embed/Object Tag Content-Disposition Bypass

Title source: llm

Description

When a file download is specified via the `Content-Disposition` header, that directive would be ignored if the file was included via a `<embed>` or `<object>` tag, potentially making a website vulnerable to a cross-site scripting attack. This vulnerability was fixed in Firefox 140, Firefox ESR 128.12, Thunderbird 140, and Thunderbird 128.12.

References (7)

Core 7

Core References

Mailing List

https://lists.debian.org/debian-lts-announce/2025/06/msg00029.html

Permissions Required

https://bugzilla.mozilla.org/show_bug.cgi?id=1971140

Vendor Advisory

https://www.mozilla.org/security/advisories/mfsa2025-51/

Vendor Advisory

https://www.mozilla.org/security/advisories/mfsa2025-53/

Mailing List

https://lists.debian.org/debian-lts-announce/2025/07/msg00002.html

Vendor Advisory

https://www.mozilla.org/security/advisories/mfsa2025-54/

Vendor Advisory

https://www.mozilla.org/security/advisories/mfsa2025-55/

Scores

CVSS v3 6.1

EPSS 0.0037

EPSS Percentile 59.0%

Attack Vector NETWORK

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N

CISA SSVC

Vulnrichment

Exploitation none

Automatable no

Technical Impact partial

Details

CWE

CWE-79

Status published

Products (6)

mozilla/firefox < 128.12.0

mozilla/firefox < 140.0

Mozilla/Firefox 128.12 - 128.*

Mozilla/Firefox 140

Mozilla/Thunderbird 128.12 - 128.*

Mozilla/Thunderbird 140

Published Jun 24, 2025

Tracked Since Feb 18, 2026