CVE-2021-21861Public exploitNetwork attack vector

Code execution via truncated hdlr allocation

Published Aug 16, 2021 · Updated Aug 3, 2024

Integer truncation in GPAC 1.0.1 allows remote attackers to execute code by convincing a user to open a crafted MPEG-4 video. In hdlr_box_read, the 64-bit hdlr atom size is truncated to 32 bits for nameUTF8 allocation, while memmove uses the truncated size minus one to copy into that undersized buffer. Exploitation requires user interaction with an attacker-supplied video and causes out-of-bounds memory access in the process context.

CVSS severity8.8
High
EPSS probability1.63%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Integer truncation in GPAC 1.0.1 allows remote attackers to execute code by convincing a user to open a crafted MPEG-4 video. In hdlr_box_read, the 64-bit hdlr atom size is truncated to 32 bits for nameUTF8 allocation, while memmove uses the truncated size minus one to copy into that undersized buffer. Exploitation requires user interaction with an attacker-supplied video and causes out-of-bounds memory access in the process context.

The record

CVE
CVE-2021-21861
Published
Aug 16, 2021
Updated
Aug 3, 2024
Vendor
GPAC Project
Product
GPAC
Classifications
CWE-680, CWE-681, T1204.002, T1203
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Aug 16, 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?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=GPAC Project Advanced Content commit a8a8d412dabcb129e695c3e7d861fcc81f608304, GPAC Project Advanced Content v1.0.1

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

GPAC Project · GPACversion=GPAC Project Advanced Content commit a8a8d412dabcb129e695c3e7d861fcc81f608304, GPAC Project Advanced Content v1.0.1

Published CVSS scores

8.8Cisco TalosCVSS:3.0/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
8.8NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
6.8NIST NVDAV: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.

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 exploitPublished

Weakness, pattern, technique

CWE-680Integer Overflow to Buffer Overflow
CWE-681Incorrect Conversion between Numeric Types
T1204.002Malicious File
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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