CVE-2021-29958

Severity: medium (CVSS 4.3 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.7% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2021-06-24 · updated 2026-06-17
Weakness: CWE-862

Description

When a download was initiated, the client did not check whether it was in normal or private browsing mode, which led to private mode cookies being shared in normal browsing mode. This vulnerability affects Firefox for iOS < 34.

Affected products

Mozilla Firefox: before 34.0 — fixed in 34.0

How to fix

Upgrade to a fixed version: Mozilla Firefox 34.0. Check the vendor advisory for mitigations.

References

https://bugzilla.mozilla.org/show_bug.cgi?id=1670127
https://www.mozilla.org/security/advisories/mfsa2021-25/
https://bugzilla.mozilla.org/show_bug.cgi?id=1670127
https://www.mozilla.org/security/advisories/mfsa2021-25/

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