What’s Vulnerable › Vulnerabilities

CVE-2021-23971

• Severity: medium (CVSS 6.5 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 1.0% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2021-02-26 · updated 2026-06-17

Description

When processing a redirect with a conflicting Referrer-Policy, Firefox would have adopted the redirect's Referrer-Policy. This would have potentially resulted in more information than intended by the original origin being provided to the destination of the redirect. This vulnerability affects Firefox < 86.

Affected products

• Mozilla Firefox: before 86.0 — fixed in 86.0

How to fix

Upgrade to a fixed version: Mozilla Firefox 86.0. Check the vendor advisory for mitigations.

References

• https://bugzilla.mozilla.org/show_bug.cgi?id=1678545
• https://security.gentoo.org/glsa/202104-10
• https://www.mozilla.org/security/advisories/mfsa2021-07/
• https://bugzilla.mozilla.org/show_bug.cgi?id=1678545
• https://security.gentoo.org/glsa/202104-10
• https://www.mozilla.org/security/advisories/mfsa2021-07/

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