Security readout for executives and security teams
Plain-English summary
This vulnerability can make Adobe Acrobat Reader DC crash when processing a malicious PDF. The main business impact is disruption to the affected user, not data theft or system takeover based on the supplied sources. It requires a crafted file scenario and is not listed as actively exploited in KEV.
Executive priority
Handle through normal patch management with some priority for PDF-heavy teams. This is a denial-of-service issue, so urgency is lower than code execution vulnerabilities, but unpatched PDF readers remain a common user-exposure surface.
Technical view
CVE-2021-35985 is a CWE-476 null pointer dereference in Acrobat Reader DC PDFLibTool handling. The supplied CVSS is 5.5 medium, with high availability impact and no confidentiality or integrity impact. The narrative says exploitation requires opening a malicious file, while the vector records UI:N/PR:L.
Likely exposure
Exposure is most likely on endpoints running Acrobat Reader DC 2021.005.20054 or earlier, 2020.004.30005 or earlier, or 2017.011.30197 or earlier. The supplied affected CPEs are unspecified, so product/version inventory is required.
Exploitation context
The supplied sources do not show active exploitation, and KEV is false. The scenario described is a malicious file causing application denial-of-service in the current user's context. No evidence supports remote code execution or privilege escalation for this CVE.
Researcher notes
The record contains a mismatch between the description's user-interaction requirement and the CVSS vector's UI:N/PR:L values. Treat user-opened malicious PDF exposure as the grounded scenario unless Adobe's bulletin clarifies otherwise. Affected version metadata is incomplete beyond version thresholds.
Mitigation direction
- Check Adobe APSB21-51 for the vendor-approved update or mitigation.
- Update affected Acrobat Reader DC installations beyond the listed vulnerable versions.
- Reduce exposure to untrusted PDFs until affected installations are updated.
- Monitor endpoint crash telemetry for repeated Acrobat Reader failures.
Validation and detection
- Inventory Acrobat Reader DC versions across managed endpoints.
- Compare installed versions with the affected version thresholds in the CVE record.
- Confirm Adobe APSB21-51 remediation has been applied where applicable.
- Review security tooling for Acrobat crash patterns, not exploit payload details.
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-2021-35985 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
- 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.