🛡️ CVE-2021-43536 on Debian — firefox-esr

⚪ Unknown ✅ No Known Exploit OSV
N/A
CVSS Score
0 Low4 Medium7 High9 Critical10

Description

Under certain circumstances, asynchronous functions could have caused a navigation to fail but expose the target URL. This vulnerability affects Thunderbird < 91.4.0, Firefox ESR < 91.4.0, and Firefox < 95.

Distribution advisory

This page covers CVE-2021-43536 as tracked by Debian, for the package firefox-esr. The fix is available in version 91.4.0esr-1; earlier versions remain affected.

How this vulnerability can be exploited

This issue can be reached over the network, attack complexity is low, an attacker needs no privileges on the target. A user must be tricked into taking some action. The scope is unchanged, so the impact stays within the vulnerable component. Rated impact: confidentiality high, integrity none, availability none.

Affected software

DEBIAN-CVE-2021-43536 is recorded against 2 packages.

  • firefox-esr (fixed in 91.4.0esr-1)
  • thunderbird (fixed in 1:91.4.0-1)

Timeline and source

Published on 8 December 2021 and last revised on 4 August 2026. No public exploit is currently recorded for this entry. Record sourced from OSV.

References

security-tracker.debian.org (Advisory)

CVE-2021-43536 on other distributions

Each distribution ships its own build and its own fixed version. Pick the one you run:

Details

Severity Unknown
CVSS Score N/A
CVSS Vector CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:N/A:N
CWE N/A
Public Exploit ✅ No
Source OSV
Published 2021-12-08
Updated 2026-08-12
Modified 2026-08-04
Fix URL N/A

Affected Packages

Software From version Fixed in
firefox-esr — 91.4.0esr-1
thunderbird — 1:91.4.0-1

Similar Threats

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