CVE-2020-21697Network attack vector

Application crash via inconsistent packet queue pointers

Published Aug 10, 2021 · Updated Aug 4, 2024

A heap use-after-free in FFmpeg 4.2 allows remote attackers to crash media-processing applications via a crafted AVI file. The mpeg_mux_write_packet function can create two packet queues when premux_packet is null while predecode_packet is not, leaving a stale pointer to freed queue storage. Exploitation requires an application to process attacker-supplied AVI content and interrupts only that application; no data disclosure or modification is reported.

CVSS severity6.5
Medium
EPSS probability0.92%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

A heap use-after-free in FFmpeg 4.2 allows remote attackers to crash media-processing applications via a crafted AVI file. The mpeg_mux_write_packet function can create two packet queues when premux_packet is null while predecode_packet is not, leaving a stale pointer to freed queue storage. Exploitation requires an application to process attacker-supplied AVI content and interrupts only that application; no data disclosure or modification is reported.

The record

CVE
CVE-2020-21697
Published
Aug 10, 2021
Updated
Aug 4, 2024
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-416, T1499.004
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Aug 10, 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

6.5NIST National Vulnerability DatabaseCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H
4.3NIST National Vulnerability DatabaseAV:N/AC:M/Au:N/C:N/I:N/A:P

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 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-416Use After Free
T1499.004Endpoint Denial of Service: Application or System Exploitation

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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