Security readout for executives and security teams
Plain-English summary
This is a low-severity Adobe Acrobat Reader DC memory disclosure issue. A user would need to open a malicious PDF for an attacker to read limited memory from that user's process. It does not provide code execution, privilege escalation, or system-wide access based on the supplied sources.
Executive priority
Treat this as routine patch management, not an emergency. Prioritize broad endpoint update coverage, especially for users who regularly receive external PDFs.
Technical view
CVE-2021-35987 is a CWE-125 out-of-bounds read in Acrobat Reader DC. Affected versions include 2021.005.20054 and earlier, 2020.004.30005 and earlier, and 2017.011.30197 and earlier. CVSS 3.1 is 3.3: local attack vector, no privileges required, user interaction required, low confidentiality impact only.
Likely exposure
Exposure is mainly user workstations running outdated Acrobat Reader DC that open PDFs from email, web downloads, shared drives, or other untrusted sources.
Exploitation context
The source bundle does not show CISA KEV listing or active exploitation evidence. Exploitation requires victim interaction by opening a malicious file, and impact is limited to memory disclosure in the current user's context.
Researcher notes
The supplied evidence supports memory disclosure only. It does not support claims of remote code execution, sandbox escape, active exploitation, or complete affected CPE coverage. Validate details against Adobe APSB21-51 before operational decisions.
Mitigation direction
- Apply Adobe guidance from APSB21-51 or current vendor update channels.
- Upgrade affected Acrobat Reader DC installations beyond the listed vulnerable versions.
- Prioritize systems handling external or untrusted PDF files.
- Reduce automatic opening of PDFs from email or web sources where feasible.
Validation and detection
- Inventory Acrobat Reader DC versions across managed endpoints.
- Compare installed versions against 2021.005.20054, 2020.004.30005, and 2017.011.30197 thresholds.
- Confirm Adobe security updates from APSB21-51 are deployed.
- Check endpoint controls for handling untrusted PDF attachments and downloads.
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
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ATT&CK lookup starting points
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CWE-125: Exact CWE lookup
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Open ATT&CK lookupCVE-2021-35987 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/apsb21-51.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.