Security readout for executives and security teams
Plain-English summary
This flaw lets a local attacker run code as the current user if they can place a file in the victim's C:/ folder and convince the victim to open a malicious file in affected Adobe Acrobat Reader versions.
Executive priority
Treat this as a high-priority endpoint hygiene issue, especially where Acrobat Reader is broadly deployed. It is not remotely exploitable by itself, but successful exploitation could execute code with the user's privileges.
Technical view
CVE-2021-28636 is a CWE-427 uncontrolled search path element issue in Acrobat Reader DC 2021.005.20054 and earlier, 2020.004.30005 and earlier, and 2017.011.30197 and earlier. The CVSS 3.1 score is 7.3. Attack complexity is low, but exploitation requires local access, low privileges, and user interaction.
Likely exposure
Exposure is most likely on Windows endpoints running the affected Acrobat Reader DC release lines where local users or attackers can write to C:/ and users may open untrusted files.
Exploitation context
The source bundle does not show CISA KEV listing or other evidence of active exploitation. The described attack requires user interaction and prior access sufficient to place content in the victim's C:/ folder.
Researcher notes
The core condition is search path control plus user-assisted file opening. Avoid assuming broader affected products or active exploitation from the provided evidence. Patch details are not included in the bundle beyond the Adobe advisory reference.
Mitigation direction
- Review Adobe APSB21-51 for vendor remediation guidance.
- Update affected Acrobat Reader installations according to Adobe guidance.
- Prevent standard users from writing files to C:/ root.
- Reduce exposure to untrusted files opened in Acrobat Reader.
- Prioritize managed Windows endpoints with older Reader DC versions.
Validation and detection
- Inventory Acrobat Reader DC versions across Windows endpoints.
- Identify systems at or below the affected version thresholds.
- Check whether non-admin users can write to C:/ root.
- Review endpoint controls for handling untrusted Reader files.
- Confirm remediation status against Adobe APSB21-51.
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-427: 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-2021-28636 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
- 7.3 (3.1)
- Known Exploited
- No
- Published
Vector: CVSS:3.1/AV:L/AC:L/PR:L/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:L/UI:R/S:U/C:H/I:H/A:H1.35.9Primary CVE scoreVulnerability scoring details
Base CVSS 3.1 score
7.3HighVector: CVSS:3.1/AV:L/AC:L/PR:L/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/apsb21-51.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.
Uncontrolled Search Path Element
Uncontrolled Search Path Element represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.