CVE-2021-29985

HIGHNVD 8.88.8—

8.8

A use-after-free vulnerability in media channels could have led to memory corruption and a potentially exploitable crash. This vulnerability affects Thunderbird < 78.13, Thunderbird < 91, Firefox ESR < 78.13, and Firefox < 91.

CVSS v3: 8.8
EG Score: 8.8(medium)
EPSS: 61.7%
KEV: Not listed

Published

August 17, 2021

Last Modified

November 21, 2024

References (14)

security@mozillahttps://bugzilla.mozilla.org/show_bug.cgi?id=1722083
security@mozillahttps://security.gentoo.org/glsa/202202-03
security@mozillahttps://security.gentoo.org/glsa/202208-14
security@mozillahttps://www.mozilla.org/security/advisories/mfsa2021-33/
security@mozillahttps://www.mozilla.org/security/advisories/mfsa2021-34/
security@mozillahttps://www.mozilla.org/security/advisories/mfsa2021-35/
security@mozillahttps://www.mozilla.org/security/advisories/mfsa2021-36/
af854a3a-2127-422b-91ae-364da2661108https://bugzilla.mozilla.org/show_bug.cgi?id=1722083
af854a3a-2127-422b-91ae-364da2661108https://security.gentoo.org/glsa/202202-03
af854a3a-2127-422b-91ae-364da2661108https://security.gentoo.org/glsa/202208-14
af854a3a-2127-422b-91ae-364da2661108https://www.mozilla.org/security/advisories/mfsa2021-33/
af854a3a-2127-422b-91ae-364da2661108https://www.mozilla.org/security/advisories/mfsa2021-34/
af854a3a-2127-422b-91ae-364da2661108https://www.mozilla.org/security/advisories/mfsa2021-35/
af854a3a-2127-422b-91ae-364da2661108https://www.mozilla.org/security/advisories/mfsa2021-36/

Patch Availability(10)

Vendor / Ecosystem	Fixed in / Patch	Released	Source
ubuntu	firefox-mozsymbols (91.0+build2-0ubuntu0.21.04.1) @ hirsute	2026-05-26	ubuntu
ubuntu	thunderbird-locale-id (1:78.13.0+build1-0ubuntu0.21.04.2) @ hirsute	2026-05-26	ubuntu
redhat	firefox-0:78.13.0-2.el7_9	2021-08-16	redhat
redhat	thunderbird-0:78.13.0-1.el7_9	2021-08-16	redhat
redhat	thunderbird-0:78.13.0-1.el8_4	2021-08-16	redhat
redhat	firefox-0:78.13.0-2.el8_4	2021-08-16	redhat
redhat	firefox-0:78.13.0-2.el8_1	2021-08-16	redhat
redhat	thunderbird-0:78.13.0-1.el8_1	2021-08-16	redhat
redhat	firefox-0:78.13.0-2.el8_2	2021-08-16	redhat
redhat	thunderbird-0:78.13.0-1.el8_2	2021-08-16	redhat

Patches are aggregated from vendor advisories (Red Hat, Microsoft, Cisco, GitHub) and package ecosystems (OSV, GHSA). Multiple rows for the same upstream release have been deduplicated.

Weakness Classification(1)

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

CWE-416Use After Free

All Vendor Advisories

(10)

Every vendor that published an advisory referencing this CVE — pulled from our cve_vendor_advisories aggregation. Click any row for the vendor's original advisory page.

Data Freshness Timeline

(refreshed 12× in last 7d / 20× in last 30d)

Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. Most recent first.

2026-06-08 14:15 UTCEPSS rescore
2026-06-07 15:23 UTCEPSS rescore
2026-06-07 15:23 UTCEPSS rescore
2026-06-06 13:46 UTCEPSS rescore
2026-06-06 13:46 UTCEPSS rescore
2026-06-06 13:46 UTCEPSS rescore
2026-06-05 22:45 UTCEPSS rescore
2026-06-05 22:45 UTCEPSS rescore
2026-06-05 06:09 UTCEPSS rescore
2026-06-05 06:09 UTCEPSS rescore
2026-06-04 13:10 UTCEPSS rescore
2026-06-04 13:10 UTCEPSS rescore
2026-06-02 20:11 UTCEPSS rescore
2026-06-02 20:11 UTCEPSS rescore
2026-06-02 20:11 UTCEPSS rescore
2026-06-01 13:50 UTCEPSS rescore
2026-06-01 13:50 UTCEPSS rescore
2026-05-31 22:29 UTCEPSS rescore
2026-05-31 22:29 UTCEPSS rescore
2026-05-31 00:15 UTCEPSS rescore

Frequently asked(5)

What is CVE-2021-29985?

CVE-2021-29985 is a high vulnerability published on August 17, 2021. A use-after-free vulnerability in media channels could have led to memory corruption and a potentially exploitable crash. This vulnerability affects Thunderbird < 78.13, Thunderbird < 91, Firefox ESR < 78.13, and Firefox < 91.

When was CVE-2021-29985 disclosed?

CVE-2021-29985 was first published in the National Vulnerability Database on August 17, 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-2021-29985 actively exploited?

CVE-2021-29985 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 61.7% percentile likelihood of exploitation in the next 30 days — higher percentiles indicate greater predicted risk.

What is the CVSS score of CVE-2021-29985?

CVE-2021-29985 has a CVSS v3 base score of 8.8 (NVD).

How do I remediate CVE-2021-29985?

Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2021-29985, 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

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CVE-2021-29985

Published

Last Modified

References (14)

Patch Availability(10)

Weakness Classification(1)

All Vendor Advisories

Data Freshness Timeline

Frequently asked(5)

Dependency Blast Radius

Is Your Infrastructure Affected by CVE-2021-29985?

Same vendor

Same CWE

CVE-2021-29985

📅 Published

🔄 Last Modified

🔗 References (14)

Patch Availability(10)

Weakness Classification(1)

All Vendor Advisories

Data Freshness Timeline

❓ Frequently asked(5)

Dependency Blast Radius

Is Your Infrastructure Affected by CVE-2021-29985?

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Frequently asked(5)

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