CVE-2025-11712

An OBJECT tag type attribute overrode browser behavior on web resources without a content-type

Published Oct 14, 2025 CVSS 3.1 · 6.1 Medium EPSS < 1% KEV · Not listed
Description
A malicious page could have used the type attribute of an OBJECT tag to override the default browser behavior when encountering a web resource served without a content-type. This could have contributed to an XSS on a site that unsafely serves files without a content-type header. This vulnerability was fixed in Firefox 144, Firefox ESR 140.4, Thunderbird 144, and Thunderbird 140.4.

Remediation

No solution or workaround provided in the CVE record

Tracking

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Advisories

Source ID Title
Debian DLA Debian DLA DLA-4335-1 firefox-esr security update
Debian DLA Debian DLA DLA-4351-1 thunderbird security update
Debian DSA Debian DSA DSA-6025-1 firefox-esr security update
Debian DSA Debian DSA DSA-6040-1 thunderbird security update
Ubuntu USN Ubuntu USN USN-7991-1 Thunderbird vulnerabilities
History
Type Values Removed Values Added
Description A malicious page could have used the type attribute of an OBJECT tag to override the default browser behavior when encountering a web resource served without a content-type. This could have contributed to an XSS on a site that unsafely serves files without a content-type header. This vulnerability affects Firefox < 144, Firefox ESR < 140.4, Thunderbird < 144, and Thunderbird < 140.4. A malicious page could have used the type attribute of an OBJECT tag to override the default browser behavior when encountering a web resource served without a content-type. This could have contributed to an XSS on a site that unsafely serves files without a content-type header. This vulnerability was fixed in Firefox 144, Firefox ESR 140.4, Thunderbird 144, and Thunderbird 140.4.
Type Values Removed Values Added
Title thunderbird: firefox: An OBJECT tag type attribute overrode browser behavior on web resources without a content-type An OBJECT tag type attribute overrode browser behavior on web resources without a content-type
Type Values Removed Values Added
First Time appeared Mozilla firefox Esr
Vendors & Products Mozilla firefox Esr
Type Values Removed Values Added
First Time appeared Mozilla
Mozilla firefox
Mozilla thunderbird
CPEs cpe:2.3:a:mozilla:firefox:*:*:*:*:-:*:*:*
cpe:2.3:a:mozilla:firefox:*:*:*:*:esr:*:*:*
cpe:2.3:a:mozilla:thunderbird:*:*:*:*:*:*:*:*
Vendors & Products Mozilla
Mozilla firefox
Mozilla thunderbird
Type Values Removed Values Added
Weaknesses CWE-116
Metrics ssvc

{'options': {'Automatable': 'no', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}

Type Values Removed Values Added
Title thunderbird: firefox: An OBJECT tag type attribute overrode browser behavior on web resources without a content-type
Weaknesses CWE-436
References
Metrics threat_severity

None

cvssV3_1

{'score': 6.1, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N'}

threat_severity

Moderate

Type Values Removed Values Added
Description A malicious page could have used the type attribute of an OBJECT tag to override the default browser behavior when encountering a web resource served without a content-type. This could have contributed to an XSS on a site that unsafely serves files without a content-type header. This vulnerability affects Firefox < 144, Firefox ESR < 140.4, Thunderbird < 144, and Thunderbird < 140.4.
References
Weaknesses

Sources

Status
PUBLISHED
Assigner
mozilla
Published
Updated
Apr 13, 2026, 2:29 PM
Reserved
Oct 13, 2025, 7:50 PM
Status
Modified
Published
Oct 14, 2025, 1:15 PM
Modified
Oct 23, 2026, 10:10 PM
Severity
Moderate
Public date
Oct 14, 2025, 12:27 PM