CVE-2021-23961

Severity: high (CVSS 7.4 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 1.5% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2021-02-26 · updated 2026-06-17

Description

Further techniques that built on the slipstream research combined with a malicious webpage could have exposed both an internal network's hosts as well as services running on the user's local machine. This vulnerability affects Firefox < 85.

Affected products

Debian Linux: 9.0, 10.0
Mozilla Firefox: before 85.0 — fixed in 85.0

How to fix

Upgrade to a fixed version: Mozilla Firefox 85.0. Check the vendor advisory for mitigations.

References

https://bugzilla.mozilla.org/show_bug.cgi?id=1677940
https://lists.debian.org/debian-lts-announce/2021/04/msg00019.html
https://lists.debian.org/debian-lts-announce/2021/04/msg00020.html
https://security.gentoo.org/glsa/202104-09
https://security.gentoo.org/glsa/202104-10
https://www.debian.org/security/2021/dsa-4895
https://www.debian.org/security/2021/dsa-4897
https://www.mozilla.org/security/advisories/mfsa2021-03/
https://bugzilla.mozilla.org/show_bug.cgi?id=1677940
https://lists.debian.org/debian-lts-announce/2021/04/msg00019.html
https://lists.debian.org/debian-lts-announce/2021/04/msg00020.html
https://security.gentoo.org/glsa/202104-09

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