Security readout for executives and security teams
Plain-English summary
Adobe Acrobat Reader had a memory-safety flaw that could let an attacker run code as the person using the computer. The victim must open a malicious file, so the main business risk is phishing or document-delivery abuse against workstations.
Executive priority
Treat this as a high-priority workstation patching issue, not an internet-facing emergency. The main urgency is reducing phishing-driven code execution risk on user devices.
Technical view
CVE-2021-28635 is a CWE-416 use-after-free in Acrobat Reader DC affecting 2021.005.20054 and earlier, 2020.004.30005 and earlier, and 2017.011.30197 and earlier. CVSS 3.1 is 7.8: local attack vector, low complexity, no privileges, user interaction required, and high confidentiality, integrity, and availability impact.
Likely exposure
Exposure is most likely on employee endpoints running affected Acrobat Reader DC versions, especially where users open PDFs from email, web downloads, shared drives, or external parties.
Exploitation context
The source bundle does not show CISA KEV listing or other evidence of active exploitation. Exploitation requires user interaction: a victim must open a malicious file.
Researcher notes
The CVSS vector indicates no privileges are needed, but user interaction is required. The bundle identifies arbitrary code execution in the current user context, but does not provide exploit details or independent exploitation reports.
Mitigation direction
- Apply Adobe guidance from APSB21-51 for Acrobat Reader.
- Update Acrobat Reader beyond the listed affected versions.
- Prioritize endpoints handling external PDFs or sensitive data.
- Restrict risky attachment handling where patching is delayed.
Validation and detection
- Inventory Acrobat Reader versions across managed endpoints.
- Compare findings against the affected version ranges in the CVE record.
- Confirm Adobe update status through endpoint management reporting.
- Review email and web controls for malicious PDF delivery 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-416: 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-2021-28635 mapping review
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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.
Use After Free
Use After Free represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.