Security readout for executives and security teams
Plain-English summary
GPAC’s MPEG-4 decoder can mishandle a malicious video file and corrupt memory. An attacker would need someone or a system to process the crafted video. Successful exploitation could affect confidentiality, integrity, and availability, matching the 8.8 high CVSS rating.
Executive priority
Treat this as a high-priority remediation item for systems that handle untrusted video. The issue is not evidenced as actively exploited in the supplied sources, but the impact is potentially full compromise of affected processing contexts.
Technical view
CVE-2021-21853 is an unchecked addition integer overflow in GPAC Project Advanced Content MPEG-4 decoding. The overflow can lead to a heap-based buffer overflow and memory corruption when parsing crafted MPEG-4 input. Reported affected versions include GPAC v1.0.1 and commit a8a8d412dabcb129e695c3e7d861fcc81f608304.
Likely exposure
Exposure is most likely where GPAC or libgpac processes MPEG-4 files, especially user-uploaded, emailed, downloaded, or externally supplied media. Desktop users, media pipelines, preview services, and content ingestion systems should be checked.
Exploitation context
The provided sources do not show CISA KEV listing or active exploitation. Exploitation requires crafted MPEG-4 content and user or system interaction to open or decode the video.
Researcher notes
Focus validation on GPAC MPEG-4 parsing paths and dependency inventory. The root class is CWE-680 integer overflow to buffer overflow. Avoid assuming broader product impact beyond GPAC unless an application’s dependency chain confirms GPAC use.
Mitigation direction
- Identify GPAC and libgpac use across workstations, servers, and media-processing pipelines.
- Check Talos and Debian DSA-4966 guidance for fixed package or upgrade direction.
- Prioritize updates where GPAC processes untrusted or externally supplied video.
- Restrict untrusted MPEG-4 processing until vendor guidance is applied.
- Ensure media ingestion services run with least privilege and isolation.
Validation and detection
- Confirm installed GPAC versions are not v1.0.1 or the affected commit.
- Review applications that link GPAC or call GPAC media-processing components.
- Check Debian-managed systems against DSA-4966 package status.
- Verify upload, preview, and transcoding workflows do not pass untrusted video to vulnerable GPAC.
- Document any compensating isolation around media-processing workloads.
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-2021-21853 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.