CVE-2021-38171Network attack vector

Unspecified impact via unchecked bit-reader initialization

Published Aug 21, 2021 · Updated Aug 4, 2024

Unchecked return handling in FFmpeg 4.4 allows attackers to cause an unspecified impact via crafted ADTS extradata. The adts_decode_extradata function passes attacker-controlled packet data to init_get_bits without checking whether bit-reader initialization failed. Reaching the flaw requires the ADTS muxer to process crafted codec extradata; neither the CVE record nor the upstream fix identifies a concrete post-failure consequence.

CVSS severity9.8
Critical
EPSS probability2.41%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Unchecked return handling in FFmpeg 4.4 allows attackers to cause an unspecified impact via crafted ADTS extradata. The adts_decode_extradata function passes attacker-controlled packet data to init_get_bits without checking whether bit-reader initialization failed. Reaching the flaw requires the ADTS muxer to process crafted codec extradata; neither the CVE record nor the upstream fix identifies a concrete post-failure consequence.

The record

CVE
CVE-2021-38171
Published
Aug 21, 2021
Updated
Aug 4, 2024
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-252
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Aug 21, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 4, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Affected buildAffected product and version details are unavailable.

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Affected products and versions are unavailable in this record.

Published CVSS scores

9.8NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-252Unchecked Return Value

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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