Security readout for executives and security teams
Plain-English summary
CVE-2021-21835 is a high-severity media parsing flaw in GPAC. A malicious MPEG-4 file can corrupt memory when opened, potentially affecting confidentiality, integrity, and availability. Business risk is highest where GPAC processes files from users, partners, or the internet.
Executive priority
Treat this as a prompt remediation item where GPAC handles external media. The likely business impact is service disruption or compromise through malicious video content. Priority is lower where GPAC is absent or only processes trusted internal media.
Technical view
The vulnerability is an integer overflow in GPAC MPEG-4 decoding for the csgp FOURCC atom. Unchecked arithmetic can produce a heap-based buffer overflow and memory corruption. The listed affected versions are GPAC Project Advanced Content v1.0.1 and commit a8a8d412dabcb129e695c3e7d861fcc81f608304.
Likely exposure
Exposure is likely limited to applications, services, or workflows that embed or invoke the affected GPAC library to decode MPEG-4 content. File upload processing, media ingestion, transcoding, or user-opened video workflows deserve review. The source bundle does not identify downstream products.
Exploitation context
The cited description says exploitation requires convincing a user to open a specially crafted video, or otherwise having an affected decoder process that file. KEV is false, and the provided sources do not state active exploitation in the wild.
Researcher notes
This is CWE-680: integer overflow to buffer overflow. Focus review on MPEG-4 csgp atom parsing, arithmetic bounds checks, allocation sizing, and heap write paths. Evidence in the bundle supports memory corruption risk but does not provide patch details or active exploitation evidence.
Mitigation direction
- Inventory software and services that include affected GPAC versions or the listed commit.
- Check GPAC or vendor guidance for fixed versions; the bundle does not name a patch.
- Restrict untrusted MPEG-4 processing until affected components are updated or isolated.
- Run media parsing in sandboxed, least-privilege environments where feasible.
- Prioritize systems that process external uploads or partner-supplied video files.
Validation and detection
- Confirm whether GPAC Project Advanced Content v1.0.1 is present in builds or dependencies.
- Check source or package metadata for commit a8a8d412dabcb129e695c3e7d861fcc81f608304.
- Map every workflow that decodes MPEG-4 files from untrusted sources.
- Verify compensating controls around media upload, decoding isolation, and crash monitoring.
- Document vendor advisory status and any fixed GPAC version once confirmed.
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-2021-21835 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
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.