Security readout for executives and security teams
Plain-English summary
A malicious PDF opened in vulnerable Adobe Acrobat Reader DC could run code as the logged-in user. This is a workstation risk, not a remote server takeover. Business urgency depends on how widely Reader is deployed and how exposed users are to untrusted PDFs.
Executive priority
Treat this as a high-priority endpoint patching issue where Adobe Reader is broadly deployed. It needs timely remediation, especially for users receiving external documents, but the source bundle does not support claiming active exploitation.
Technical view
CVE-2021-21036 is a CWE-190 integer overflow in Adobe Acrobat Reader DC. The CVSS 3.1 score is 7.8 with local attack vector, no privileges required, required user interaction, and high confidentiality, integrity, and availability impact.
Likely exposure
Endpoints running Acrobat Reader DC 2020.013.20074 or earlier, 2020.001.30018 or earlier, or 2017.011.30188 or earlier are potentially exposed when users open untrusted files.
Exploitation context
The provided sources do not show CISA KEV listing or active exploitation. Exploitation requires a victim to open a malicious file, after which code could execute in that user’s context.
Researcher notes
The key constraints are AV:L and UI:R: exploitation depends on local file handling by a user. The impact is high because successful exploitation can execute code as the current user. The bundle does not provide exploit details or specific fixed versions beyond Adobe’s advisory reference.
Mitigation direction
- Inventory Acrobat Reader DC installations and versions across managed endpoints.
- Review and apply Adobe APSB21-09 guidance for affected Reader DC installations.
- Prioritize users who routinely handle external PDFs or email attachments.
- Restrict or warn on untrusted PDF attachments until remediation is complete.
- Ensure endpoint protections monitor suspicious Reader child processes.
Validation and detection
- Compare installed Reader DC versions against the affected version thresholds.
- Confirm patched or vendor-approved versions after software deployment.
- Verify high-risk user groups are included in the endpoint inventory.
- Review mail and web controls for untrusted PDF delivery exposure.
- Check EDR telemetry for unusual Acrobat Reader process behavior.
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-190: 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-2021-21036 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/apsb21-09.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.
Integer Overflow or Wraparound
Integer Overflow or Wraparound represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.