Security readout for executives and security teams
Plain-English summary
CVE-2021-21839 affects GPAC’s MPEG-4 decoding. A malicious video file can trigger memory corruption when opened, potentially allowing serious impact to confidentiality, integrity, and availability. The known trigger requires user interaction, so exposure is highest where GPAC handles untrusted media.
Executive priority
Treat as high priority for environments that process external video. The business risk is compromise through malicious media, but urgency is lower than a wormable server flaw because user interaction is documented.
Technical view
The issue is multiple integer overflows in GPAC Project Advanced Content v1.0.1 and commit a8a8d412. Unchecked arithmetic during MPEG-4 input handling can lead to heap-based buffer overflow and memory corruption. It is classified as CWE-680 with CVSS 3.0 score 8.8.
Likely exposure
Systems using affected GPAC/libgpac versions to open, inspect, transcode, or otherwise process MPEG-4 files are the likely exposure. Risk increases where users or automated workflows handle untrusted video content.
Exploitation context
The source bundle says exploitation requires a specially crafted MPEG-4 input and convincing a user to open a video. KEV is false, and no cited source in the bundle confirms active exploitation.
Researcher notes
Evidence supports memory corruption from malformed MPEG-4 parsing in affected GPAC versions. The bundle does not provide exploit availability, fixed upstream version details, or proof of active attacks, so avoid claims beyond the cited Talos, CVE, and Debian materials.
Mitigation direction
- Update GPAC or distribution packages using vendor guidance, including Debian DSA-4966 where applicable.
- Avoid opening untrusted MPEG-4 files with affected GPAC builds until remediated.
- Isolate or sandbox media-processing workflows that must handle external video files.
- Check upstream GPAC and operating-system advisories for fixed versions and backports.
Validation and detection
- Inventory GPAC/libgpac versions and compare against v1.0.1 and the cited affected commit.
- Review SBOMs and bundled dependencies for embedded GPAC copies.
- Identify endpoints or services that process user-supplied MPEG-4 files.
- Confirm applicable Debian systems have applied DSA-4966 package updates.
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
Use these exact CWE pages and searches to review the Glexia ATT&CK library from this CVE's weakness and description context.
CWE-680: Exact CWE lookup
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Open ATT&CK lookupCVE-2021-21839 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-2021-1297CVE reference · x_refsource_MISC
- DSA-4966CVE reference · vendor-advisory, x_refsource_DEBIAN
- https://www.talosintelligence.com/vulnerability_reports/TALOS-2021-1297CVE 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.