Security readout for executives and security teams
Plain-English summary
CVE-2021-21854 is a high-severity flaw in GPAC MPEG-4 decoding. A malicious video file can trigger memory corruption when a user or automated workflow opens it, potentially affecting confidentiality, integrity, and availability.
Executive priority
Treat this as a timely patching and exposure-reduction item for media-processing environments. Urgency rises if GPAC handles externally supplied video files or automated ingestion.
Technical view
The issue is an unchecked addition integer overflow in GPAC Project Advanced Content v1.0.1 and commit a8a8d412dabcb129e695c3e7d861fcc81f608304. The overflow can become a heap-based buffer overflow during MPEG-4 parsing, causing memory corruption.
Likely exposure
Exposure is most likely where GPAC or libgpac is used to parse, preview, ingest, transcode, or otherwise process MPEG-4 media, especially from untrusted or user-supplied sources.
Exploitation context
The source bundle says exploitation requires convincing a user to open a crafted MPEG-4 input. CISA KEV is false, and the provided sources do not establish active exploitation.
Researcher notes
CWE-680 fits the described integer-overflow-to-buffer-overflow chain. CVSS 8.8 reflects low attack complexity, no privileges, required user interaction, and high impact across confidentiality, integrity, and availability.
Mitigation direction
- Identify GPAC and libgpac installations and embedded dependencies.
- Apply applicable vendor or distribution updates, including Debian DSA-4966 where relevant.
- Avoid opening or processing untrusted MPEG-4 files until remediated.
- Restrict media ingestion workflows to trusted sources where practical.
- Run media parsing services with least privilege and isolation.
Validation and detection
- Check installed GPAC or libgpac versions against affected versions.
- Review containers, build manifests, and media-processing hosts for GPAC usage.
- Confirm Debian systems have incorporated DSA-4966 updates where applicable.
- Map workflows that accept MPEG-4 files from users or external parties.
- Use version and configuration checks rather than crafted malicious media.
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-2021-21854 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
- 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.