Security readout for executives and security teams
Plain-English summary
CVE-2026-27821 is a high-severity crash risk in GPAC, an open-source multimedia framework. A specially crafted NHML file can overflow a stack buffer while being parsed, potentially causing service disruption. The public advisory identifies affected versions up to and including 26.02.0 and points to a patch commit.
Executive priority
Prioritize remediation for internet-facing or untrusted-file media processing environments. The main documented business impact is availability disruption from crafted input. Treat as high priority where GPAC is used in automated ingestion, transcoding, or content-processing services.
Technical view
The GPAC NHML demuxer in src/filters/dmx_nhml.c copies the xmlHeaderEnd attribute into a fixed 1000-byte stack buffer using strcpy() without length validation. Overlong input can overwrite stack memory. The issue is classified as CWE-121 with CVSS 4.0 score 7.7 and patched by commit 9bd7137fded2db40de61a2cf3045812c8741ec52.
Likely exposure
Exposure is likely where GPAC versions <= 26.02.0 process NHML or untrusted multimedia inputs. Risk is higher for automated media pipelines, upload workflows, transcoding services, or analysis systems that accept externally supplied files.
Exploitation context
The CVSS vector indicates network attackability, low complexity, no privileges, and no user interaction, with high availability impact. The source bundle does not show CISA KEV listing or public active exploitation evidence, so active exploitation should not be assumed.
Researcher notes
Evidence is limited to the CVE record, GitHub advisory, and patch commit. The described vulnerable pattern is a straightforward stack buffer overflow in NHML attribute handling. Sources support denial-of-service impact; they do not establish active exploitation or broader product impact beyond GPAC.
Mitigation direction
- Upgrade GPAC to a version containing commit 9bd7137fded2db40de61a2cf3045812c8741ec52 or later.
- If immediate upgrade is not possible, restrict processing of untrusted NHML files.
- Reduce exposure of GPAC-backed media processing services to untrusted network sources.
- Monitor GPAC advisory and release notes for official patched release guidance.
Validation and detection
- Inventory GPAC installations and embedded GPAC libraries across media workflows.
- Confirm deployed versions are not <= 26.02.0, or include the patch commit.
- Review pipelines for NHML parsing or automated handling of untrusted media files.
- Check crash telemetry around GPAC NHML parsing for unusual availability events.
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-121: Exact CWE lookup
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Open ATT&CK lookupCVE-2026-27821 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
- 7.7 (4.0)
- Known Exploited
- No
- Published
Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:P
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:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:P——Primary CVE scoreVulnerability scoring details
Base CVSS 4.0 score
7.7HighVector: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:P
Source materials
- CVE List V5 sourceCVE List V5
- https://github.com/gpac/gpac/security/advisories/GHSA-q7qh-8r2r-q559CVE reference · x_refsource_CONFIRM
- https://github.com/gpac/gpac/commit/9bd7137fded2db40de61a2cf3045812c8741ec52CVE 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.
Stack-based Buffer Overflow
Stack-based Buffer Overflow represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.