Security readout for executives and security teams
Plain-English summary
This is a high-impact Adobe Acrobat Reader flaw that can let a malicious PDF run code as the person who opens it. The attack needs user interaction, so exposure is driven by endpoints that receive or open untrusted PDF files.
Executive priority
Treat this as a high-priority endpoint patching issue, not a confirmed active campaign. The business risk is code execution through malicious documents, especially in teams processing external PDFs.
Technical view
CVE-2021-39841 is a CWE-843 type confusion issue in Acrobat Reader DC affecting 2021.005.20060 and earlier, 2020.004.30006 and earlier, and 2017.011.30199 and earlier. Successful exploitation can execute arbitrary code in the current user's context after a malicious file is opened.
Likely exposure
Likely exposure is workstation-focused: users running affected Acrobat Reader DC versions, especially those handling PDFs from email, web downloads, portals, or external parties. Source data does not provide CPEs or full fixed-version details.
Exploitation context
The source states exploitation requires user interaction: a victim must open a malicious file. KEV status is false, and the provided sources do not cite active exploitation.
Researcher notes
The title references Acrobat Pro DC DocMedia, while the description and affected entry reference Acrobat Reader DC. Confirm exact product scope and fixed versions in Adobe APSB21-55 before closing exposure.
Mitigation direction
- Apply Adobe guidance from APSB21-55 for affected Acrobat Reader installations.
- Inventory endpoints for affected 2021, 2020, and 2017 Acrobat Reader DC branches.
- Prioritize users who open externally supplied PDFs.
- Harden email and web controls for suspicious PDF attachments and downloads.
- Check vendor guidance before assuming compensating controls are sufficient.
Validation and detection
- Confirm installed Acrobat Reader versions are newer than affected versions listed in the CVE.
- Verify patch deployment coverage across managed endpoints.
- Review software inventory for legacy 2017, 2020, and 2021 Reader branches.
- Check security telemetry for suspicious Acrobat child processes or alerts.
- Document any unsupported or unmanaged Acrobat installations.
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-843: Exact CWE lookup
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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-2021-39841 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 (3.0)
- Known Exploited
- No
- Published
Vector: CVSS:3.0/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:3.0/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H1.85.9Primary CVE scoreVulnerability scoring details
Base CVSS 3.0 score
7.8HighVector: CVSS:3.0/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/acrobat/apsb21-55.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 Resource Using Incompatible Type ('Type Confusion')
Access of Resource Using Incompatible Type ('Type Confusion') represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.