CVE-2021-4140 | BDVDB-2026-191249 Detail

MozillaFirefox ESR

Description#

It was possible to construct specific XSLT markup that would be able to bypass an iframe sandbox. This vulnerability affects Firefox ESR < 91.5, Firefox < 96, and Thunderbird < 91.5.

Impact#

Per CVSS v3.1: confidentiality impact high, integrity impact high, availability impact high. Attack vector: network.

Weaknesses#

CWE-91 XML Injection (aka Blind XPath Injection)

References#

Exploit#

No public exploit known

History#

Version 12022-12-22Record published in the CVE List.
Version 22025-04-16Most recent update recorded in the CVE List.

Published

Published: 2022-12-22
Last modified: 2025-04-16

Vendor information

Vendor: Mozilla
Product: Firefox ESR

All Mozilla vulnerabilities

Score

9.8 Critical

EPSS

1.4%, Low

Estimated chance of exploitation in the next 30 days. EPSS percentile: 72.8.

KEV

Not listed in the CISA Known Exploited Vulnerabilities catalog.

Impact

Not classified

Action

No specific action is recorded in the source data. Check the references for vendor guidance.

Affected Systems

Vulnerable
< 91.5
Fixed
91.5

Scoring System

CVSS v4.0

Not available

CVSS v3.1

9.8 Critical

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

Metric breakdown
Attack Vector	Network
Attack Complexity	Low
Privileges Required	None
User Interaction	None
Scope	Unchanged
Confidentiality	High
Integrity	High
Availability	High

CVSS v3.0

Not available

CVSS v2

Not available

Source: CVE List v5 (record); CISA KEV (kev, action); FIRST EPSS (epss).