CVE-2021-29958

MEDIUMNVD 4.34.3—

4.3

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.

CVSS v3: 4.3
EG Score: 4.3(medium)
EPSS: 40.2%
KEV: Not listed

Published

June 24, 2021

Last Modified

November 21, 2024

References (4)

security@mozillahttps://bugzilla.mozilla.org/show_bug.cgi?id=1670127
security@mozillahttps://www.mozilla.org/security/advisories/mfsa2021-25/
af854a3a-2127-422b-91ae-364da2661108https://bugzilla.mozilla.org/show_bug.cgi?id=1670127
af854a3a-2127-422b-91ae-364da2661108https://www.mozilla.org/security/advisories/mfsa2021-25/

Weakness Classification(2)

MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.

Data Freshness Timeline

(refreshed 11× in last 7d / 20× in last 30d)

Every time one of our enrichment pipelines (NVD, MITRE cvelistV5, EPSS, CISA KEV, GHSA, OSV, vendor advisories) ran against this CVE. Most recent first.

2026-06-04 13:10 UTCepss_batch
2026-06-04 13:10 UTCepss_batch
2026-06-02 20:11 UTCepss_batch
2026-06-02 20:11 UTCepss_batch
2026-06-02 20:11 UTCepss_batch
2026-06-01 13:50 UTCepss_batch
2026-06-01 13:50 UTCepss_batch
2026-05-31 22:29 UTCepss_batch
2026-05-31 22:29 UTCepss_batch
2026-05-31 00:15 UTCepss_batch
2026-05-29 13:42 UTCepss_batch
2026-05-28 13:43 UTCepss_batch
2026-05-28 13:43 UTCepss_batch
2026-05-27 13:39 UTCepss_batch
2026-05-27 13:39 UTCepss_batch
2026-05-26 14:30 UTCEG score recompute
2026-05-26 14:30 UTCGHSA enrichment
2026-05-26 13:42 UTCepss_batch
2026-05-26 07:17 UTCepss_batch
2026-05-26 07:17 UTCepss_batch

Frequently asked(5)

What is CVE-2021-29958?

CVE-2021-29958 is a medium vulnerability published on June 24, 2021. 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.

When was CVE-2021-29958 disclosed?

CVE-2021-29958 was first published in the National Vulnerability Database on June 24, 2021, with the most recent update on November 21, 2024. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.

Is CVE-2021-29958 actively exploited?

CVE-2021-29958 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 40.2% percentile likelihood of exploitation in the next 30 days — higher percentiles indicate greater predicted risk.

What is the CVSS score of CVE-2021-29958?

CVE-2021-29958 has a CVSS v3 base score of 4.3 (NVD).

How do I remediate CVE-2021-29958?

Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2021-29958, EchelonGraph cross-links them in the Vendor Advisories panel below — those typically contain the canonical remediation steps, fixed version numbers, and any vendor-specific mitigations.

Dependency Blast Radius

See which npm, PyPI, Go, and Maven packages are affected by CVE-2021-29958

Explore →

Is Your Infrastructure Affected by CVE-2021-29958?

EchelonGraph automatically scans your cloud infrastructure and maps CVE exposure using blast radius analysis.

Start Free Scan →Browse All CVEs

CVE-2021-29958

📅 Published

🔄 Last Modified

🔗 References (4)

Weakness Classification(2)

Data Freshness Timeline

❓ Frequently asked(5)

Dependency Blast Radius

Is Your Infrastructure Affected by CVE-2021-29958?

🔗 Related CVEs(same CWE)

Same CWE

Published

Last Modified

References (4)

Frequently asked(5)

Related CVEs(same CWE)