Security readout for executives and security teams
Plain-English summary
This flaw lets a malicious TIFF file crash or take over Adobe InDesign with the rights of the person who opens it. It requires user interaction, so exposure is mainly through files received by designers, marketing teams, publishers, or vendors.
Executive priority
Treat this as a high-priority desktop application risk for creative and publishing users. It is not described as remotely exploitable without user action, but a successful attack could compromise workstations through normal file-opening workflows.
Technical view
CVE-2021-39820 is a CWE-787 out-of-bounds write in Adobe InDesign TIFF handling. A crafted TIFF can cause memory corruption and potential arbitrary code execution as the current user. CVSS 3.1 is 7.8 with user interaction required and high confidentiality, integrity, and availability impact.
Likely exposure
Organizations are exposed where Adobe InDesign 16.3, 16.3.1, or earlier versions are installed and users open external or untrusted TIFF content. Systems used for publishing, creative production, marketing, and document intake are the most likely affected assets.
Exploitation context
The provided sources do not show CISA KEV listing or active exploitation. Exploitation requires a user to open a malicious TIFF in an affected InDesign version. The risk remains meaningful because successful exploitation can execute code as that user.
Researcher notes
Evidence is limited to the CVE record and Adobe advisory reference. The sources identify affected InDesign versions, CWE-787, malicious TIFF handling, arbitrary code execution potential, and required user interaction. They do not provide active exploitation evidence in the supplied bundle.
Mitigation direction
- Check Adobe APSB21-73 for the vendor-provided update or remediation guidance.
- Upgrade or remove affected Adobe InDesign versions where vendor guidance requires it.
- Limit opening TIFF files from untrusted senders until remediation is complete.
- Use email, web, and endpoint controls to quarantine suspicious image attachments.
- Prioritize remediation on shared creative workstations and high-privilege user systems.
Validation and detection
- Inventory endpoints for Adobe InDesign 16.3, 16.3.1, and earlier installations.
- Confirm remediated systems no longer run versions listed as affected.
- Review file-intake workflows that allow external TIFF files into creative teams.
- Check security tooling for detections involving suspicious TIFF delivery to InDesign users.
- Document residual exposure where legacy InDesign versions remain necessary.
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-2021-39820 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.
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:H1.85.9Primary CVE scoreVulnerability 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
Source materials
- CVE List V5 sourceCVE List V5
- https://helpx.adobe.com/security/products/indesign/apsb21-73.htmlCVE reference · 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.