Cyber Resilience

CVE-2021-43543

Medium

Published: 08 December 2021

Published
08 December 2021
Modified
21 November 2024
KEV Added
—
Patch
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CVSS Score v3.1 6.1 CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
EPSS Score 0.0046 64.6th percentile
Risk Priority 12 60% EPSS · 20% KEV · 20% CVSS

Summary

CVE-2021-43543 is a medium-severity Cross-site Scripting (CWE-79) vulnerability in Debian Debian Linux. Its CVSS base score is 6.1 (Medium).

Operationally, ranked in the top 35.4% of CVEs by exploit likelihood; it is not currently listed in the CISA KEV catalog.

EU & UK References

Vulnerability details

Documents loaded with the CSP sandbox directive could have escaped the sandbox's script restriction by embedding additional content. This vulnerability affects Thunderbird < 91.4.0, Firefox ESR < 91.4.0, and Firefox < 95.

CWE(s)
CWE-79

Related Threats

No named actor attribution yet. ATT&CK technique mapping in progress for this CVE.

Affected Assets

mozilla
firefox
≤ 95.0
mozilla
firefox esr
≤ 91.4.0
mozilla
thunderbird
≤ 91.4.0
debian
debian linux
10.0, 11.0, 9.0

Mitigating Controls

Likely Mitigating Controls AI

Per-CVE control mapping for this CVE has not run yet; the list below is derived from the weakness types (CWEs) cited in the NVD entry.

CA-8 Penetration Testing
addresses: CWE-79

Penetration testing submits XSS payloads to web applications, detecting cross-site scripting flaws for subsequent remediation.

SI-10 Information Input Validation
addresses: CWE-79

Validates web inputs to reject script-related content that could produce XSS.

SI-15 Information Output Filtering
addresses: CWE-79

Output validation against expected content can reject or sanitize script content in generated web pages, reducing XSS exploitability.

References