How severe is CVE-2021-38171?

CVE-2021-38171 has a CVSS 3.x base score of 9.8, rated critical severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.

Is CVE-2021-38171 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 2% (82nd percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2021-38171?

CVE-2021-38171 primarily affects Ffmpeg. In total, 4 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.

How do I fix CVE-2021-38171?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its critical severity, prioritise patching exposed systems.

When was CVE-2021-38171 published?

CVE-2021-38171 was published on 2021-08-21 and last updated on 2026-06-17.

CVE-2021-38171

CVE-2021-38171 is a critical-severity vulnerability in Ffmpeg with a CVSS 3.x base score of 9.8. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-252.

Key facts

Severity: Critical (CVSS 3.x base score 9.8)
CVSS v2: 7.5
EPSS exploit prediction: 2% (82nd percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-252
Affected product: Ffmpeg
Published: 2021-08-21
Last modified: 2026-06-17

Description

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.

Frequently asked questions

What is CVE-2021-38171?: 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.
How severe is CVE-2021-38171?: CVE-2021-38171 has a CVSS 3.x base score of 9.8, rated critical severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.
Is CVE-2021-38171 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 2% (82nd percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2021-38171?: CVE-2021-38171 primarily affects Ffmpeg. In total, 4 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2021-38171?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its critical severity, prioritise patching exposed systems.
When was CVE-2021-38171 published?: CVE-2021-38171 was published on 2021-08-21 and last updated on 2026-06-17.

References

Affected products (4)

cpe:2.3:a:ffmpeg:ffmpeg:4.4:*:*:*:*:*:*:*
cpe:2.3:o:debian:debian_linux:9.0:*:*:*:*:*:*:*
cpe:2.3:o:debian:debian_linux:10.0:*:*:*:*:*:*:*
cpe:2.3:o:debian:debian_linux:11.0:*:*:*:*:*:*:*

More vulnerabilities in Ffmpeg

CVE-2013-0864 — Critical (CVSS 10.0): The gif_copy_img_rect function in libavcodec/gifdec.c in FFmpeg before 1.1.2 performs an incorrect calculation for an…
CVE-2013-4265 — Critical (CVSS 10.0): The av_reallocp_array function in libavutil/mem.c in FFmpeg before 2.0.1 has an unspecified impact and remote vectors…
CVE-2013-0873 — Critical (CVSS 10.0): The read_header function in libavcodec/shorten.c in FFmpeg before 1.1.3 allows remote attackers to have an unspecified…
CVE-2013-0872 — Critical (CVSS 10.0): The swr_init function in libswresample/swresample.c in FFmpeg before 1.1.3 allows remote attackers to have an…
CVE-2011-3937 — Critical (CVSS 10.0): The H.263 codec (libavcodec/h263dec.c) in FFmpeg 0.7.x before 0.7.12, 0.8.x before 0.8.11, and unspecified versions…
CVE-2012-2804 — Critical (CVSS 10.0): Unspecified vulnerability in libavcodec/indeo3.c in FFmpeg before 0.11 and Libav 0.8.x before 0.8.5 has unknown impact…

All CVEs affecting Ffmpeg →

Other CWE-252 vulnerabilities

CVE-2025-66565 — Critical (CVSS 9.8): Fiber Utils is a collection of common functions created for Fiber. In versions 2.0.0-rc.3 and below, when the system's…
CVE-2021-26955 — Critical (CVSS 9.8): An issue was discovered in the xcb crate through 2021-02-04 for Rust. It has a soundness violation because…
CVE-1999-0199 — Critical (CVSS 9.8): manual/search.texi in the GNU C Library (aka glibc) before 2.2 lacks a statement about the unspecified tdelete return…
CVE-2019-15900 — Critical (CVSS 9.8): An issue was discovered in slicer69 doas before 6.2 on certain platforms other than OpenBSD. On platforms without…
CVE-2010-0211 — Critical (CVSS 9.8): The slap_modrdn2mods function in modrdn.c in OpenLDAP 2.4.22 does not check the return value of a call to the…
CVE-2007-3798 — Critical (CVSS 9.8): Integer overflow in print-bgp.c in the BGP dissector in tcpdump 3.9.6 and earlier allows remote attackers to execute…

Browse all CWE-252 vulnerabilities →