Security readout for executives and security teams
Plain-English summary
A malicious PDF could cause Adobe Acrobat Reader DC to read memory it should not access, potentially exposing limited information from the current user's session. The issue requires someone to open the malicious file, and the published CVSS score is low.
Executive priority
Treat this as routine patching, not an emergency, unless high-risk users handle large volumes of unsolicited PDFs. The business risk is limited information disclosure, but PDF-reader vulnerabilities are still worth closing promptly.
Technical view
CVE-2021-39844 is a CWE-125 out-of-bounds read in Adobe Acrobat Reader DC CalRGB handling. Affected versions include 2021.005.20060 and earlier, 2020.004.30006 and earlier, and 2017.011.30199 and earlier. Impact is limited to confidentiality in the current user context.
Likely exposure
Exposure is most likely on user workstations running the affected Acrobat Reader DC release lines, especially where staff regularly receive or download untrusted PDFs. Server-side exposure is not indicated by the supplied sources.
Exploitation context
The sources state exploitation requires user interaction: a victim must open a malicious file. The CVE is not listed as KEV in the supplied bundle, so there is no source-grounded evidence here of known active exploitation.
Researcher notes
Evidence is limited to the CVE record and Adobe advisory reference in the bundle. No exploit details, active exploitation claim, or independent mitigation details are provided. Avoid assuming impact beyond local, user-assisted memory disclosure.
Mitigation direction
- Apply Adobe security updates referenced in APSB21-55.
- Check Adobe guidance for exact fixed versions per release track.
- Prioritize endpoints that process external PDFs frequently.
- Use attachment filtering and user warnings for untrusted PDFs.
Validation and detection
- Inventory Acrobat Reader DC versions across managed endpoints.
- Flag versions 2021.005.20060, 2020.004.30006, 2017.011.30199, and earlier.
- Confirm patched endpoints report updated Acrobat Reader DC versions.
- Review PDF-handling endpoints with high external document exposure.
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-125: Exact CWE lookup
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Open ATT&CK lookupCVE-2021-39844 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
- Low
- CVSS
- 3.3 (3.1)
- Known Exploited
- No
- Published
Vector: CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:L/I:N/A:N
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:L/I:N/A:N1.81.4Primary CVE scoreVulnerability scoring details
Base CVSS 3.1 score
3.3LowVector: CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:L/I:N/A:N
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.
Out-of-bounds Read
Out-of-bounds Read represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.