CVE-2021-4140
CriticalPublic PoC
Published: 22 December 2022
Published
22 December 2022
Modified
16 April 2025
KEV Added
—
Patch
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CVSS Score v3.1
10.0
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H
EPSS Score
0.0006
20.3th percentile
Risk Priority
20
60% EPSS · 20% KEV · 20% CVSS
Summary
CVE-2021-4140 is a critical-severity aka Blind XPath Injection (CWE-91) vulnerability in Mozilla Firefox. Its CVSS base score is 10.0 (Critical).
Operationally, ranked at the 20.3th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog; a public proof-of-concept is referenced.
EU & UK References
- 🇪🇺 ENISA EUVD: EUVD-2021-34009
Vulnerability details
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.
- CWE(s)
Related Threats
No named actor attribution yet. ATT&CK technique mapping in progress for this CVE.
Affected Assets
mozilla
firefox
≤ 96.0
mozilla
firefox esr
≤ 91.5
mozilla
thunderbird
≤ 91.5
Mitigating Controls
No mitigating controls mapped yet. The per-CVE control annotator has not reached this CVE.