Security readout for executives and security teams
Plain-English summary
A malicious MPEG-4 video can trigger memory corruption in GPAC v1.0.1 when decoded. The attacker must get someone or a system using GPAC to open the file. Impact is high because memory corruption can affect confidentiality, integrity, and availability.
Executive priority
Prioritize remediation on systems that process external media, especially shared workstations and automated media services. Treat as high urgency where GPAC handles untrusted files, but do not claim active exploitation without additional evidence.
Technical view
CVE-2021-21847 is an unchecked arithmetic issue in GPAC MPEG-4 “stts” decoding. Integer overflow can lead to a heap-based buffer overflow and memory corruption. Sources identify GPAC Project Advanced Content v1.0.1 and commit a8a8d412dabcb129e695c3e7d861fcc81f608304 as affected.
Likely exposure
Exposure is most likely where GPAC or applications embedding GPAC decode MPEG-4 content from users, email, downloads, or media workflows. The source bundle does not enumerate downstream products, so asset owners should confirm direct GPAC use and packaged dependencies.
Exploitation context
The CVE requires user interaction: an attacker convinces a user to open a crafted video. The bundle does not show CISA KEV listing or other evidence of active exploitation, so active exploitation should not be assumed.
Researcher notes
The key security condition is integer overflow during “stts” MPEG-4 decoding leading to heap buffer overflow. Evidence is specific to GPAC v1.0.1 and one commit. Downstream application impact must be validated through dependency analysis.
Mitigation direction
- Check GPAC and distribution advisories for fixed versions.
- Apply Debian DSA-4966 updates where Debian packages are used.
- Reduce GPAC exposure to untrusted MPEG-4 files.
- Isolate media decoding workflows from sensitive systems.
- Avoid automatically opening or previewing untrusted videos.
Validation and detection
- Inventory GPAC, libgpac, and dependent media applications.
- Check for GPAC v1.0.1 or the affected commit.
- Review media upload, preview, and transcoding paths.
- Confirm Debian systems received DSA-4966 security updates.
- Document any compensating isolation around media decoding.
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
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ATT&CK lookup starting points
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Open ATT&CK lookupCVE-2021-21847 mapping review
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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.