Security readout for executives and security teams
Plain-English summary
This Adobe Acrobat Reader DC flaw can let an attacker run code as the person using the computer if they open a malicious PDF or file. It is serious because successful exploitation could compromise documents, install malware, or support broader endpoint intrusion.
Executive priority
Treat this as a high-priority endpoint patching issue, especially where staff frequently open externally supplied PDFs. It is not confirmed as actively exploited in the provided sources, but the impact is full code execution after user interaction.
Technical view
CVE-2021-21035 is a CWE-416 use-after-free vulnerability in Acrobat Reader DC. The CVSS 3.0 score is 8.8. An unauthenticated attacker can achieve arbitrary code execution in the current user's context, but exploitation requires user interaction by opening a malicious file.
Likely exposure
Exposure is likely on endpoints running Acrobat Reader DC 2020.013.20074 or earlier, 2020.001.30018 or earlier, or 2017.011.30188 or earlier. The bundle does not provide CPEs or deployment-specific product variants beyond Acrobat Reader.
Exploitation context
The source bundle does not show CISA KEV listing or other evidence of active exploitation. The credible attack path is social delivery of a malicious file that a user opens, leading to code execution with that user's privileges.
Researcher notes
Evidence is limited to CVE data and Adobe's advisory reference. The bundle provides affected version thresholds and CVSS vector, but not exploit telemetry, proof-of-concept status, CPEs, or detailed fixed-version mapping.
Mitigation direction
- Apply Adobe guidance and updates from APSB21-09.
- Inventory Acrobat Reader versions across managed endpoints.
- Prioritize users who frequently receive external PDFs.
- Use endpoint controls to reduce untrusted document execution risk.
- Monitor vendor guidance for any additional remediation details.
Validation and detection
- Check installed Acrobat Reader DC versions against affected thresholds.
- Confirm patched builds are deployed after applying APSB21-09 guidance.
- Review endpoint telemetry for suspicious document-opening events.
- Verify controls for handling externally sourced PDF files.
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-2021-21035 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.