CVE-2020-21688Network attack vector

Code execution via misclassified RTP hint stream

Published Aug 10, 2021 · Updated Aug 4, 2024

Heap use-after-free in the MOV muxer in FFmpeg 4.2 allows remote attackers to execute arbitrary code by remuxing a crafted RTP hint stream. mov_get_codec_tag preserves the input's "rtp " tag, so the muxer treats the stream as internally owned and mov_free releases codecpar without clearing st->codecpar. Processing attacker-supplied media with the MOV muxer and user interaction are required; successful exploitation runs code in the FFmpeg process context.

CVSS severity8.8
High
EPSS probability1.73%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Heap use-after-free in the MOV muxer in FFmpeg 4.2 allows remote attackers to execute arbitrary code by remuxing a crafted RTP hint stream. mov_get_codec_tag preserves the input's "rtp " tag, so the muxer treats the stream as internally owned and mov_free releases codecpar without clearing st->codecpar. Processing attacker-supplied media with the MOV muxer and user interaction are required; successful exploitation runs code in the FFmpeg process context.

The record

CVE
CVE-2020-21688
Published
Aug 10, 2021
Updated
Aug 4, 2024
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-416, T1203
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

6.8NIST NVDAV:N/AC:M/Au:N/C:P/I:P/A:P
8.8NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:R/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.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

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-416Use After Free
T1203Exploitation for Client Execution

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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