Security readout for executives and security teams
Plain-English summary
CVE-2021-28637 is a high-severity Adobe Acrobat Reader DC flaw triggered when a user opens a malicious PDF. Successful exploitation runs in the current user’s context and could expose or alter sensitive information. The bundle does not show active exploitation or a CISA KEV listing.
Executive priority
Treat as a high-priority workstation patching issue, especially for users who receive external PDFs. It requires user interaction, which lowers urgency versus wormable flaws, but successful exploitation can affect confidentiality, integrity, and availability under the user account.
Technical view
The vulnerability is an out-of-bounds read in Acrobat Reader DC affecting versions 2021.005.20054 and earlier, 2020.004.30005 and earlier, and 2017.011.30197 and earlier. CVSS 3.1 is 7.8 with local attack vector, no privileges required, required user interaction, and high confidentiality, integrity, and availability impact.
Likely exposure
Organizations are exposed where users can open PDFs with affected Acrobat Reader DC versions installed. Exposure is most relevant on workstations handling email attachments, downloaded PDFs, or shared documents from untrusted sources.
Exploitation context
The attacker must persuade a user to open a malicious file. The source bundle does not identify public exploitation, in-the-wild attacks, or inclusion in CISA KEV.
Researcher notes
Evidence is limited to the CVE record and Adobe advisory reference. The provided affected product entry names Acrobat Reader, while the title mentions Acrobat Pro DC PDFLibTool. Do not broaden affected products beyond Adobe’s advisory without additional vendor confirmation.
Mitigation direction
- Check Adobe APSB21-51 for the vendor-supported update path.
- Update affected Acrobat Reader DC installations per Adobe guidance.
- Reduce handling of untrusted PDFs on unpatched workstations.
- Use endpoint and email controls to block suspicious PDF delivery.
- Prioritize systems used by high-risk staff and document-heavy workflows.
Validation and detection
- Inventory Acrobat Reader DC versions across managed endpoints.
- Flag versions at or below the affected release thresholds.
- Confirm remediation status against Adobe APSB21-51 guidance.
- Review whether high-risk users still run affected builds.
- Document compensating controls where updates are delayed.
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-125: 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-2021-28637 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/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.