CVE-2021-38171

CRITICALNVD 9.89.8—

9.8

adts_decode_extradata in libavformat/adtsenc.c in FFmpeg 4.4 does not check the init_get_bits return value, which is a necessary step because the second argument to init_get_bits can be crafted.

CVSS v3: 9.8
EG Score: 9.8(medium)
EPSS: 43.3%
KEV: Not listed

Published

August 21, 2021

Last Modified

November 21, 2024

References (12)

cve@mitrehttps://github.com/FFmpeg/FFmpeg/commit/9ffa49496d1aae4cbbb387aac28a9e061a6ab0a6
cve@mitrehttps://lists.debian.org/debian-lts-announce/2021/11/msg00012.html
cve@mitrehttps://patchwork.ffmpeg.org/project/ffmpeg/patch/AS8P193MB12542A86E22F8207EC971930B6F19%40AS8P193MB1254.EURP193.PROD.OUTLOOK.COM/
cve@mitrehttps://security.gentoo.org/glsa/202312-14
cve@mitrehttps://www.debian.org/security/2021/dsa-4990
cve@mitrehttps://www.debian.org/security/2021/dsa-4998
af854a3a-2127-422b-91ae-364da2661108https://github.com/FFmpeg/FFmpeg/commit/9ffa49496d1aae4cbbb387aac28a9e061a6ab0a6
af854a3a-2127-422b-91ae-364da2661108https://lists.debian.org/debian-lts-announce/2021/11/msg00012.html
af854a3a-2127-422b-91ae-364da2661108https://patchwork.ffmpeg.org/project/ffmpeg/patch/AS8P193MB12542A86E22F8207EC971930B6F19%40AS8P193MB1254.EURP193.PROD.OUTLOOK.COM/
af854a3a-2127-422b-91ae-364da2661108https://security.gentoo.org/glsa/202312-14
af854a3a-2127-422b-91ae-364da2661108https://www.debian.org/security/2021/dsa-4990
af854a3a-2127-422b-91ae-364da2661108https://www.debian.org/security/2021/dsa-4998

Patch Availability(2)

Vendor / Ecosystem	Fixed in / Patch	Released	Source
ubuntu	libavdevice-dev (7:4.4.2-0ubuntu0.22.04.1) @ jammy	2026-05-26	ubuntu
ubuntu	libavdevice-ffmpeg56 (7:2.8.17-0ubuntu0.1+esm4) @ xenial	2026-05-26	ubuntu

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-252Unchecked Return Value

All Vendor Advisories

(2)

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 10× in last 7d / 10× 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.

2026-05-27 13:39 UTCepss_batch
2026-05-27 13:39 UTCepss_batch
2026-05-27 13:39 UTCepss_batch
2026-05-26 13:42 UTCepss_batch
2026-05-26 11:44 UTCEG score recompute
2026-05-26 11:44 UTCVendor advisory
2026-05-26 11:44 UTCGHSA enrichment
2026-05-26 07:17 UTCepss_batch
2026-05-26 07:17 UTCepss_batch
2026-05-26 07:17 UTCepss_batch

Frequently asked(5)

What is CVE-2021-38171?

CVE-2021-38171 is a critical vulnerability published on August 21, 2021. adtsdecodeextradata in libavformat/adtsenc.c in FFmpeg 4.4 does not check the initgetbits return value, which is a necessary step because the second argument to initgetbits can be crafted.

When was CVE-2021-38171 disclosed?

CVE-2021-38171 was first published in the National Vulnerability Database on August 21, 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-2021-38171 actively exploited?

CVE-2021-38171 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 43.3% percentile likelihood of exploitation in the next 30 days — higher percentiles indicate greater predicted risk.

What is the CVSS score of CVE-2021-38171?

CVE-2021-38171 has a CVSS v3 base score of 9.8 (NVD).

How do I remediate CVE-2021-38171?

Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2021-38171, 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-2021-38171

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