Security readout for executives and security teams
Plain-English summary
A malicious PDF or similar file could make Adobe Acrobat Reader run attacker-controlled code as the person who opened it. This is a user-interaction issue, but CISA lists it as known exploited, so unpatched Reader installations should be treated as urgent exposure.
Executive priority
Treat this as a high-priority endpoint patching issue because it is critical severity, supports code execution, and is listed as known exploited by CISA. Business urgency depends on how widely Adobe Reader is deployed and how quickly endpoints can be updated.
Technical view
CVE-2021-28550 is a CWE-416 use-after-free in Adobe Acrobat Reader DC. A remote unauthenticated attacker can achieve arbitrary code execution in the current user context if the victim opens a malicious file. CVSS is 9.6 with high confidentiality, integrity, and availability impact.
Likely exposure
Exposure is likely on endpoints with Acrobat Reader DC 2021.001.20150 or earlier, 2020.001.30020 or earlier, or 2017.011.30194 or earlier. Risk is highest where PDFs from email, browsers, or external parties are routinely opened.
Exploitation context
Active exploitation is supported by CISA KEV listing. The provided sources do not describe exploit volume, affected industries, or exploitation details. Exploitation requires user interaction: a victim must open a malicious file.
Researcher notes
The supplied evidence identifies affected Reader version thresholds, CWE-416, CVSS 9.6, user interaction requirements, and KEV status. It does not provide root-cause details, exploit primitives, indicators of compromise, or a detailed fixed-version matrix beyond the Adobe advisory reference.
Mitigation direction
- Apply Adobe Acrobat Reader updates referenced by APSB21-29.
- Remove or upgrade Reader versions at or below the affected version thresholds.
- Prioritize remediation on email-heavy and internet-facing user workstations.
- Use vendor guidance for any compensating controls or deployment constraints.
- Track remediation against CISA KEV requirements where applicable.
Validation and detection
- Inventory Adobe Acrobat Reader versions across managed endpoints.
- Confirm no systems remain on affected Reader version thresholds or earlier.
- Verify patch deployment status in endpoint management tooling.
- Review email and endpoint alerts for suspicious PDF delivery or Reader crashes.
- Document any exceptions with owner, business reason, and remediation date.
Public sources used
Michael Williams reviewed this cited source version on .
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-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-2021-28550 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
- Critical
- CVSS
- 9.6 (3.0)
- Known Exploited
- Yes
- Published
Vector: CVSS:3.0/AV:N/AC:L/PR:N/UI:R/S:C/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.
CISA KEV status
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:N/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:H2.86Primary CVE scoreVulnerability scoring details
Base CVSS 3.0 score
9.6CriticalVector: CVSS:3.0/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:H
Source materials
- CVE List V5 sourceCVE List V5
- https://helpx.adobe.com/security/products/acrobat/apsb21-29.htmlCVE reference
- https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-28550CVE reference · government-resource
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.