Security readout for executives and security teams
Plain-English summary
This flaw affects Adobe InCopy 11.1 and earlier. A malicious TIFF file can trigger memory corruption and may let an attacker run code as the user who opens it. The business risk is highest where staff handle externally supplied publishing assets or email attachments.
Executive priority
Treat this as a high-priority workstation exposure, especially for creative teams. It is not described as remotely wormable, but successful exploitation could give an attacker the user’s access and data reach.
Technical view
CVE-2021-39818 is a CWE-788 memory corruption issue in Adobe InCopy caused by insecure handling of a malicious TIFF file. CVSS 3.1 is 7.8 high, with local attack vector, low complexity, no privileges required, and required user interaction.
Likely exposure
Likely exposure is limited to endpoints running Adobe InCopy 11.1 or earlier, especially in editorial, design, marketing, or publishing workflows that ingest third-party TIFF files.
Exploitation context
The source bundle does not show CISA KEV listing or active exploitation. Exploitation requires user interaction and would execute code in the context of the current user, not automatically over the network.
Researcher notes
The bundle identifies InCopy 11.1 and earlier, malicious TIFF handling, CWE-788, and CVSS 7.8. It does not provide proof-of-concept status, exploit telemetry, or detailed fixed-version data beyond the Adobe advisory reference.
Mitigation direction
- Inventory Adobe InCopy installations and identify versions 11.1 or earlier.
- Review Adobe APSB21-71 for vendor-provided update or remediation guidance.
- Prioritize updates on systems processing external publishing assets.
- Restrict handling of untrusted TIFF files until vendor remediation is confirmed.
- Use least-privilege user accounts for desktop publishing workstations.
Validation and detection
- Confirm installed Adobe InCopy versions across managed endpoints.
- Check whether affected systems have been updated according to APSB21-71.
- Review mail, web, and file-ingestion workflows for untrusted TIFF exposure.
- Verify endpoint protection covers suspicious document-processing child processes.
- Document exceptions where legacy InCopy remains business-critical.
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
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CWE-788: 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-2021-39818 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/incopy/apsb21-71.htmlCVE 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.
Access of Memory Location After End of Buffer
Access of Memory Location After End of Buffer represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.