Security readout for executives and security teams
Plain-English summary
A malicious MPEG-4 video can crash or potentially compromise software using the affected GPAC decoding library. The user or service must open/process the file. Sources rate this high severity, but do not show CISA KEV listing or confirmed active exploitation.
Executive priority
Treat as high priority where GPAC processes untrusted video content. Business urgency is lower for systems without GPAC or without MPEG-4 ingestion from users, partners, or email/web sources.
Technical view
CVE-2021-21856 covers multiple integer overflows in GPAC Project Advanced Content v1.0.1 and commit a8a8d412. Unchecked addition during MPEG-4 decoding can lead to heap-based buffer overflow and memory corruption. CVSS is 8.8 with user interaction required.
Likely exposure
Exposure is most likely in applications, desktop tools, or media-processing services that embed GPAC v1.0.1 or the named commit and parse MPEG-4 input. The provided sources do not identify other affected products.
Exploitation context
The attack scenario requires a specially crafted MPEG-4 input and a victim action or workflow that opens/processes it. The bundle marks KEV as false, so active exploitation is not established by the provided evidence.
Researcher notes
The key uncertainty is remediation detail: the provided bundle names the vulnerable versions and Talos report, but does not include a specific fixed release. Validate exact GPAC provenance before declaring systems affected or remediated.
Mitigation direction
- Inventory applications and services that include GPAC Advanced Content.
- Check GPAC or vendor guidance for fixed versions or patches.
- Avoid processing untrusted MPEG-4 files with affected GPAC builds.
- Isolate media parsing workflows if remediation cannot be confirmed.
- Prioritize systems handling external uploads or email-delivered videos.
Validation and detection
- Search SBOMs and dependency records for GPAC v1.0.1.
- Check build metadata for commit a8a8d412dabcb129e695c3e7d861fcc81f608304.
- Identify workflows that decode user-supplied MPEG-4 content.
- Confirm whether affected systems run vendor-remediated GPAC builds.
- Document remaining exposure where external media processing continues.
Public sources used
Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.
Conservative CVE-to-ATT&CK context
These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.
ATT&CK lookup starting points
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CWE-680: Exact CWE lookup
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Open ATT&CK lookupCVE-2021-21856 mapping review
Open the CVE-to-ATT&CK bridge for reviewed, inferred, or future official mappings tied to this CVE.
Open ATT&CK lookup- Severity
- High
- CVSS
- 8.8 (3.0)
- Known Exploited
- No
- Published
Vector: CVSS:3.0/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
CNA and ADP enrichment extracted from CVE v5
These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.
CVSS vector scores
1 official scoreWe collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.
CVSS:3.0/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H2.85.9Primary CVE scoreVulnerability scoring details
Base CVSS 3.0 score
8.8HighVector: CVSS:3.0/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
Source materials
- CVE List V5 sourceCVE List V5
- https://talosintelligence.com/vulnerability_reports/TALOS-2021-1299CVE reference · x_refsource_MISC
Products and packages named in the record
CWE details
CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.
Integer Overflow to Buffer Overflow
Integer Overflow to Buffer Overflow represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.