CVE-2021-32439Public exploit

Code execution via unchecked packed-sample count

Published Aug 11, 2021 · Updated Aug 3, 2024

Buffer overflow in GPAC 1.0.1 MP4Box allows attackers to execute arbitrary code or crash the application via a crafted media file. The stbl_AppendSize function accepts a packed-sample count with the high bit set, uses it in sample-table allocation arithmetic, and writes beyond the allocated size array. Exploitation requires a victim to run MP4Box's hinting operation on the file; the published proof of concept demonstrates the out-of-bounds write and crash.

CVSS severity7.8
High
EPSS probability1.27%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Buffer overflow in GPAC 1.0.1 MP4Box allows attackers to execute arbitrary code or crash the application via a crafted media file. The stbl_AppendSize function accepts a packed-sample count with the high bit set, uses it in sample-table allocation arithmetic, and writes beyond the allocated size array. Exploitation requires a victim to run MP4Box's hinting operation on the file; the published proof of concept demonstrates the out-of-bounds write and crash.

The record

CVE
CVE-2021-32439
Published
Aug 11, 2021
Updated
Aug 3, 2024
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-120, T1203
Attack vector
local
Privileges
unauthenticated

Timeline

How it unfolded

  1. Aug 11, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 3, 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 vectorlocal
Required privilegesunauthenticated

What is affected?

Affected products and versions are unavailable in this record.

Published CVSS scores

7.8NVDCVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
6.8NVDAV:N/AC:M/Au:N/C:P/I:P/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 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectorlocal
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-120Buffer Copy without Checking Size of Input ('Classic Buffer Overflow')
T1203Exploitation for Client Execution

Public exploit references

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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