Security readout for executives and security teams
Plain-English summary
A malicious project file opened in Adobe Substance 3D Stager could corrupt memory and run attacker-controlled code with the victim’s account permissions. The attack requires someone to open the file, making phishing, shared assets, and downloaded design files the most plausible delivery routes.
Executive priority
Treat this as a high-priority endpoint remediation issue, especially for design teams handling third-party assets. User interaction reduces immediate exposure, but successful exploitation can compromise the user’s data and workstation. Prioritize inventory, updating, and controls around externally sourced Stager files.
Technical view
CVE-2026-21342 is an out-of-bounds write (CWE-787) affecting Substance 3D Stager 3.1.6 and earlier. Successful exploitation may execute arbitrary code as the current user, with high confidentiality, integrity, and availability impact. CVSS 3.1 rates it 7.8: local attack vector, low complexity, no prior privileges, and required user interaction.
Likely exposure
Exposure is concentrated among endpoints running Substance 3D Stager 3.1.6 or earlier, particularly where users receive project files from external, shared, or untrusted sources. Systems without the product, or with versions later than the affected range, are not identified as vulnerable by the supplied description.
Exploitation context
A victim must open a malicious file locally. No privileges are required before that interaction, and successful code runs as the current user. The bundle marks this CVE as absent from KEV and cites no active exploitation; that does not establish that exploitation is impossible or has never occurred.
Researcher notes
The core primitive is an out-of-bounds write triggered through malicious file processing. The supplied evidence does not identify the vulnerable parser, file format, crash characteristics, proof of concept, or exploitation in the wild. The affected-version description states 3.1.6 and earlier; consult Adobe’s advisory for authoritative release guidance.
Mitigation direction
- Identify and prioritize Substance 3D Stager installations running version 3.1.6 or earlier.
- Update affected installations to a vendor-supported version outside the affected range.
- Confirm the appropriate release and deployment guidance in Adobe’s security advisory.
- Restrict or scrutinize Stager files received through email, downloads, and external collaboration channels.
Validation and detection
- Inventory installed Substance 3D Stager versions across managed endpoints.
- Verify affected systems no longer run version 3.1.6 or earlier.
- Review software deployment records for successful updates and unresolved failures.
- Check security telemetry for suspicious processes launched around Stager file-opening 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-787: 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 lookupExecution behavior lookup
The CVE wording references code or command execution, so execution technique review may help defensive triage. This is a Glexia inferred lookup path, not an official MITRE, ATT&CK, or CVE Program mapping.
Open ATT&CK lookupCVE-2026-21342 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
- 7.8 (3.1)
- Known Exploited
- No
- Published
Vector: CVSS:3.1/AV:L/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.
SSVC decision data
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:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H1.85.9adobeVulnerability scoring details
Base CVSS 3.1 score
7.8HighVector: CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
Vulnerability timeline
Timeline events are normalized from CVE metadata, CNA source timelines, ADP timelines, and KEV metadata when present.
- CVE reservedCVE Program
The CVE ID was reserved by the assigning CNA.
- CVE publishedCVE Program
The CVE record was published.
- CVE updatedCVE Program
The CVE record metadata indicates this as the latest update time.
ADP provider summaries
Source materials
- CVE List V5 sourceCVE List V5
- https://helpx.adobe.com/security/products/substance3d_stager/apsb26-20.htmlCVE reference, adobe · vendor-advisory
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.
Out-of-bounds Write
Out-of-bounds Write represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.