CVE-2025-11712

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

MEDIUM
6.1
CVSS Score
Published: October 14, 2025 at 12:27 PM UTC
Updated: October 23, 2026 at 10:10 PM UTC
2 products affected across 1 vendorFirefoxThunderbird

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Severity
MEDIUM6.1
Exploit prediction
EPSS 0.2%
SSVC
No known exploit

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.

Affected

Our own answer: ranges merged, affected separated from platform-only, with confidence and review flags.

v < 140.4.0v < 144.0
Vendor states this is fixed in 140.4 (unaffected)
Vendor states this is fixed in 144 (unaffected)
v < 140.4.0141.0 ≤ v < 144.0
Vendor states this is fixed in 140.4 (unaffected)
Vendor states this is fixed in 144 (unaffected)

References (7)

SSVC — Action Prioritization

SSVCNo known exploitNot automatablePartial impact

SSVC signals action urgency (what to patch first), separate from CVSS which measures severity.

CVSS

6.1MEDIUMCISA-ADP
Attack Vector
NETWORK
Complexity
LOW
Privileges
NONE
User Interaction
REQUIRED
Scope
CHANGED
Confidentiality
LOW
Integrity
LOW
Availability
NONE
Vector?

Quick Info

StatusMODIFIED
CWE
CWE-116

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