Security readout for executives and security teams
Plain-English summary
This flaw lets a malicious MPEG-4 file corrupt memory in GPAC’s decoding library when a user or service opens the file. Business risk is highest where GPAC processes untrusted media, such as upload, preview, or transcoding workflows. The sources do not show active exploitation.
Executive priority
Treat this as a high-priority remediation for any service that accepts or processes external video. The issue can affect confidentiality, integrity, and availability, but exploitation evidence is not shown in the provided sources.
Technical view
CVE-2021-21842 is an integer overflow in GPAC Project Advanced Content v1.0.1 and commit a8a8d412. Processing an MPEG-4 atom with the ssix FOURCC can cause unchecked arithmetic, leading to heap-based buffer overflow and memory corruption. CVSS is 8.8 with user interaction required.
Likely exposure
Exposure is likely in systems that run GPAC or GPAC-linked tooling to parse, decode, inspect, or transform MPEG-4 files. Public-facing media upload pipelines and internal video processing services deserve priority review. Downstream product exposure is not identified in the provided sources.
Exploitation context
The described attack requires a specially crafted MPEG-4 file and a victim user or service opening or processing it. The bundle marks KEV as false, and no cited source in the bundle claims active exploitation.
Researcher notes
Focus validation on GPAC MPEG-4 parsing paths and ssix atom handling. The root weakness is CWE-680: integer overflow leading to buffer overflow. Evidence supports GPAC v1.0.1 and the cited commit only; avoid broad downstream claims without separate vendor evidence.
Mitigation direction
- Update GPAC or distribution packages according to GPAC and Debian advisories.
- Reduce or pause GPAC processing of untrusted MPEG-4 files until remediated.
- Run media parsing in isolated, least-privileged environments.
- Apply vendor guidance rather than relying on file extension filtering.
- Track Debian DSA-4966 and GPAC advisory status for fixed package details.
Validation and detection
- Inventory GPAC binaries, libraries, containers, and packages in media-processing paths.
- Compare deployed GPAC versions against v1.0.1 and the cited affected commit.
- Identify workflows that process user-supplied MPEG-4 content.
- Confirm patched packages are deployed on Debian-managed systems.
- Review crash telemetry for GPAC memory corruption during MPEG-4 handling.
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
Use the exact CWE identifier as the starting point before reviewing related ATT&CK behavior. Open the exact CWE lookup page first, then review the ATT&CK searches from that MITRE weakness context. This is a Glexia lookup hint, not an official ATT&CK mapping.
Open ATT&CK lookupCVE-2021-21842 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
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.