Security readout for executives and security teams
Plain-English summary
CVE-2021-21059 is a high-severity Adobe Acrobat Reader DC flaw triggered when a user opens a malicious PDF. Successful exploitation could run code as that user, creating risk of data theft, malware execution, or workstation compromise.
Executive priority
Prioritize normal high-severity desktop patching. The risk is meaningful because PDF handling is common and exploitation can execute code, but the source requires user interaction and provides no evidence of active exploitation.
Technical view
The source describes a memory corruption vulnerability, mapped to CWE-787, in Acrobat Reader DC PDF parsing. It affects versions 2020.013.20074 and earlier, 2020.001.30018 and earlier, and 2017.011.30188 and earlier. CVSS 3.0 is 7.8 with local attack vector and required user interaction.
Likely exposure
Organizations are exposed where affected Acrobat Reader DC versions remain installed on endpoints, especially users handling PDFs from email, web downloads, or external parties. The bundle does not identify affected operating systems or fixed versions.
Exploitation context
The provided sources do not show CISA KEV listing or active exploitation. Exploitation requires user interaction: a victim must open a specially crafted PDF. No authentication or prior privileges are required, and impact is in the current user's context.
Researcher notes
Evidence is limited to CVE metadata and Adobe's advisory reference. The CVSS vector indicates AV:L, AC:L, PR:N, UI:R, S:U, and high confidentiality, integrity, and availability impact. Do not assume broader Adobe products, platforms, exploit maturity, or fixed versions beyond the cited sources.
Mitigation direction
- Review Adobe APSB21-09 for vendor remediation guidance.
- Update affected Acrobat Reader DC installations per Adobe guidance.
- Limit exposure to untrusted PDFs until remediation is complete.
- Use endpoint controls to reduce impact of user-context code execution.
Validation and detection
- Inventory Acrobat Reader DC versions across managed endpoints.
- Flag versions 2020.013.20074, 2020.001.30018, 2017.011.30188, and earlier.
- Confirm update status against Adobe APSB21-09 guidance.
- Review email and web controls for untrusted PDF handling.
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-787: 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-2021-21059 mapping review
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Open ATT&CK lookup- Severity
- High
- CVSS
- 7.8 (3.0)
- Known Exploited
- No
- Published
Vector: CVSS:3.0/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:3.0/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H1.85.9Primary CVE scoreVulnerability scoring details
Base CVSS 3.0 score
7.8HighVector: CVSS:3.0/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.
Out-of-bounds Write
Out-of-bounds Write represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.