Security readout for executives and security teams
Plain-English summary
This vulnerability can crash Adobe Acrobat Reader DC when a user opens a malicious file. It does not indicate data theft or system takeover in the provided sources, but it can disrupt users and workflows that depend on Reader.
Executive priority
Treat as a moderate endpoint reliability risk. It is not described as code execution or data compromise, but affected user populations should be updated through standard patch management.
Technical view
CVE-2021-39852 is a CWE-476 null pointer dereference in Acrobat Reader DC. Affected versions include 2021.005.20060 and earlier, 2020.004.30006 and earlier, and 2017.011.30199 and earlier. CVSS 3.1 is 5.5 with user interaction required and availability impact only.
Likely exposure
Exposure is mainly endpoint-based: users running affected Acrobat Reader DC versions who open attacker-supplied files. The source bundle does not identify server-side exposure or affected products beyond Acrobat Reader DC.
Exploitation context
The CVE requires user interaction because the victim must open a malicious file. The source bundle and KEV status do not support claims of active exploitation.
Researcher notes
Evidence supports an unauthenticated, user-assisted application denial-of-service via null pointer dereference. No exploit details, active exploitation evidence, or specific fixed version is included in the supplied bundle.
Mitigation direction
- Check Adobe APSB21-55 for the vendor-supported update or remediation path.
- Prioritize remediation for endpoints running affected Acrobat Reader DC versions.
- Reduce exposure to untrusted files through mail and web filtering controls.
- Use user awareness messaging for unexpected file attachments until remediated.
Validation and detection
- Inventory Acrobat Reader DC versions across managed endpoints.
- Flag versions 2021.005.20060, 2020.004.30006, 2017.011.30199, and earlier.
- Confirm whether Adobe APSB21-55 remediation has been applied.
- Review endpoint crash reports for Reader availability issues if business impact is suspected.
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
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CWE-476: Exact CWE lookup
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Open ATT&CK lookupCVE-2021-39852 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:N/UI:R/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:N/UI:R/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:N/UI:R/S:U/C:N/I:N/A:H
Source materials
- CVE List V5 sourceCVE List V5
- https://helpx.adobe.com/security/products/acrobat/apsb21-55.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.