Security readout for executives and security teams
Plain-English summary
CVE-2021-21858 is a high-severity flaw in GPAC MPEG-4 decoding. A malicious video file can trigger memory corruption if opened or processed by an affected GPAC version, potentially allowing serious confidentiality, integrity, and availability impact.
Executive priority
Treat this as high priority where GPAC handles untrusted video. It is less urgent for environments without GPAC or without external MPEG-4 processing, but still warrants inventory and patch confirmation.
Technical view
The issue is multiple integer overflows in GPAC Project Advanced Content MPEG-4 decoding. Unchecked addition arithmetic can cause a heap-based buffer overflow and memory corruption. The supplied CVSS 3.0 score is 8.8 with user interaction required.
Likely exposure
Exposure is likely on systems, applications, or media-processing pipelines using GPAC v1.0.1 or the listed affected commit. Risk is higher where users open external videos or services decode uploaded MPEG-4 content.
Exploitation context
The bundle does not show CISA KEV listing or active exploitation. The described attack requires convincing a user to open a crafted video, or reaching a service that automatically processes attacker-supplied MPEG-4 media.
Researcher notes
Evidence identifies CWE-680 integer overflow leading to heap buffer overflow in GPAC MPEG-4 decoding. Sources do not provide active exploitation evidence. Fixed-version details are incomplete in the bundle, so rely on vendor and distribution advisories for remediation mapping.
Mitigation direction
- Inventory GPAC and libgpac usage across servers, workstations, and media-processing applications.
- Apply GPAC updates from the vendor or operating-system distributor, including Debian guidance where applicable.
- Restrict or sandbox processing of untrusted MPEG-4 files until affected systems are remediated.
- Limit automatic media decoding for files from external users or untrusted sources.
- Monitor GPAC and distribution advisories for confirmed fixed versions and backports.
Validation and detection
- Check installed GPAC versions against v1.0.1 and the affected commit listed in the CVE bundle.
- Confirm Debian systems have applied the relevant DSA-4966 package updates.
- Review applications for bundled or statically linked GPAC components.
- Identify workflows that decode user-uploaded or externally received MPEG-4 files.
- Verify media-processing jobs run with isolation and least privilege.
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-2021-21858 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.