Security readout for executives and security teams
Plain-English summary
This is a denial-of-service flaw in Adobe Acrobat Reader DC. A logged-in attacker on an affected system could crash the application in the current user's context. The source bundle does not support data theft, privilege escalation, remote compromise, or active exploitation.
Executive priority
Treat as a routine but real endpoint availability risk. It should be handled through normal patch management, with faster attention where PDF workflows are business-critical or where shared systems have many authenticated users.
Technical view
CVE-2021-35984 is a CWE-476 null pointer dereference in Adobe Acrobat Reader DC PDFLibTool handling. CVSS 3.1 is 5.5: local attack vector, low complexity, low privileges required, no user interaction, unchanged scope, and high availability impact only.
Likely exposure
Exposure is limited to systems running Acrobat Reader DC 2021.005.20054 and earlier, 2020.004.30005 and earlier, or 2017.011.30197 and earlier. The attacker must already be authenticated locally according to the CVSS vector and description.
Exploitation context
The bundle says exploitation does not require user interaction, but requires authenticated local access. KEV is false, and no cited source states active exploitation. The expected impact is application denial of service, not system compromise.
Researcher notes
Evidence supports a local authenticated denial-of-service issue caused by null pointer dereference. Do not assume remote exploitation, confidentiality impact, integrity impact, or public weaponization from this bundle. Exact fixed versions should be verified in Adobe APSB21-51.
Mitigation direction
- Check Adobe APSB21-51 for the vendor-provided update guidance.
- Update affected Acrobat Reader DC installations beyond the listed vulnerable versions.
- Prioritize shared workstations and systems supporting critical document workflows.
- Restrict local account access where Acrobat availability is operationally important.
Validation and detection
- Inventory Acrobat Reader DC versions across managed endpoints.
- Flag versions at or below 2021.005.20054, 2020.004.30005, or 2017.011.30197.
- Confirm remediation status against Adobe APSB21-51 guidance.
- Review endpoint reports for repeated Acrobat crashes on vulnerable versions.
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-476: Exact CWE lookup
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Open ATT&CK lookupCVE-2021-35984 mapping review
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Open ATT&CK lookup- Severity
- Medium
- CVSS
- 5.5 (3.1)
- Known Exploited
- No
- Published
Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/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:L/UI:N/S:U/C:N/I:N/A:H1.83.6Primary CVE scoreVulnerability scoring details
Base CVSS 3.1 score
5.5MediumVector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
Source materials
- CVE List V5 sourceCVE List V5
- https://helpx.adobe.com/security/products/acrobat/apsb21-51.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.
NULL Pointer Dereference
NULL Pointer Dereference represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.