Security readout for executives and security teams
Plain-English summary
This is a memory-safety flaw in Adobe Acrobat Reader DC. If a user opens a malicious file, an attacker could run code with that user's permissions. The business risk is endpoint compromise, data access, and disruption tied to what the affected user account can reach.
Executive priority
Treat as a high-priority endpoint patching issue, not a confirmed active-exploitation emergency based on the supplied evidence. Prioritize broad workstation remediation because user interaction through malicious documents is a common enterprise risk path.
Technical view
CVE-2021-21021 is a CWE-416 use-after-free in Acrobat Reader DC versions 2020.013.20074 and earlier, 2020.001.30018 and earlier, and 2017.011.30188 and earlier. CVSS is 8.8. Exploitation requires user interaction and may allow arbitrary code execution as the current user.
Likely exposure
Exposure is most likely on user workstations running affected Acrobat Reader DC versions, especially where staff open external PDFs or email attachments. The provided sources do not indicate a server-side exposure path.
Exploitation context
The source bundle states exploitation requires a victim to open a malicious file. It is not listed as CISA KEV, and the provided sources do not establish active exploitation.
Researcher notes
The record provides vulnerability class, affected version thresholds, CVSS vector, and user-interaction requirement. It does not provide exploit details, proof of exploitation, or standalone mitigations beyond consulting Adobe's advisory.
Mitigation direction
- Check Adobe APSB21-09 for vendor update guidance.
- Upgrade affected Acrobat Reader DC installations per Adobe guidance.
- Prioritize users who handle external documents or email attachments.
- Use endpoint controls to restrict untrusted document execution paths.
Validation and detection
- Inventory Acrobat Reader DC versions across managed endpoints.
- Flag versions at or below the affected builds.
- Confirm patched systems no longer report affected versions.
- Review security tooling for malicious document detections.
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-2021-21021 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
- 8.8 (3.0)
- Known Exploited
- No
- Published
Vector: CVSS:3.0/AV:N/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:3.0/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H2.85.9Primary CVE scoreVulnerability scoring details
Base CVSS 3.0 score
8.8HighVector: CVSS:3.0/AV:N/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/apsb21-09.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.