Security readout for executives and security teams
Plain-English summary
A malicious MPEG-4 video can corrupt memory in affected GPAC decoding code if a user or service opens it. The issue is high impact because successful exploitation could affect confidentiality, integrity, and availability, but user interaction or media-processing exposure is required.
Executive priority
Prioritize remediation where GPAC processes files from customers, partners, email, or the public internet. Desktop-only exposure is still important, but business urgency is highest for automated media pipelines handling untrusted content.
Technical view
CVE-2021-21857 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. Sources identify GPAC v1.0.1 and commit a8a8d412dabcb129e695c3e7d861fcc81f608304 as affected. CWE-680 applies.
Likely exposure
Exposure is most likely where GPAC parses untrusted MPEG-4 files: media workflows, upload processing, transcoding, preview generation, or user desktops opening external videos. Confirm actual GPAC use before prioritizing broadly.
Exploitation context
The provided CVSS vector is network-adjacent in delivery but requires user interaction. The source bundle does not show CISA KEV listing or cited evidence of active exploitation. Treat exploitation status as unconfirmed.
Researcher notes
Evidence supports a memory-safety flaw triggered by specially crafted MPEG-4 input. Do not assume active exploitation from the provided bundle. Focus validation on dependency reachability and file-ingestion paths, not just package presence.
Mitigation direction
- Inventory GPAC usage in packages, containers, applications, and media-processing services.
- For Debian systems, review and apply DSA-4966 guidance where applicable.
- Upgrade or replace affected GPAC v1.0.1 or the named vulnerable commit.
- Restrict untrusted MPEG-4 processing until vendor guidance is applied.
- Check upstream GPAC guidance if your distribution is not Debian.
Validation and detection
- Confirm installed GPAC versions and build commits against the affected entries.
- Review SBOMs and dependency manifests for GPAC or Advanced Content components.
- Identify services or workflows that automatically parse uploaded MPEG-4 files.
- Check crash telemetry for GPAC MPEG-4 decoder memory-corruption failures.
- Verify Debian package remediation status against DSA-4966 where relevant.
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-2021-21857 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.