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Fencer Intel
medium 4.3

CVE-2021-29958 json

When a download was initiated, the client did not check whether it was in normal or private browsing mode, which led to private mode cookie…

published 5y ago modified 4mo ago also EUVD-2021-16417

cvss
4.3
version 3.1, NVD
cisa kev
Not listed
not in CISA's catalog
epss
0.7%
EPSS 0.7% chance of exploitation in 30 days, percentile 52%
public exploits
0
none known

Summary

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.

Patch / fix

  • Mozilla Firefox for iOS 34

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Exploit prediction

0.67% chance of exploitation in the next 30 days, higher than 52% of all scored CVEs (FIRST EPSS, 2026-11-09).

CVSS scores

assigned by version score vector
NVD 3.1 4.3 CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:N/A:N
NVD 2.0 4.3 AV:N/AC:M/Au:N/C:P/I:N/A:N

Affected products

  • Mozilla Firefox for iOS

Classification

Weakness

References

Sources

Fencer Intel keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.