Security readout for executives and security teams
Plain-English summary
CVE-2021-34851 is a high-severity Foxit PDF Reader flaw that can let an attacker run code when a user opens a malicious file or visits a malicious page. The issue affects Foxit PDF Reader 11.0.0.49893. Business risk is highest where Foxit is widely deployed and users receive untrusted PDFs.
Executive priority
Prioritize remediation on user workstations that process external PDFs. This is not listed as actively exploited in the provided sources, but the impact is full code execution after user interaction, making it important for phishing-exposed environments.
Technical view
The flaw is in Foxit PDF Reader handling of Annotation objects. Sources describe missing validation that an object exists before operations are performed, mapped to CWE-416. Successful exploitation can execute code in the current process context. CVSS 3.0 is 7.8 with local attack vector and required user interaction.
Likely exposure
Exposure is limited to installations of Foxit PDF Reader 11.0.0.49893 identified in the source bundle. Organizations should verify managed and unmanaged endpoints, especially workstations handling external PDFs, email attachments, browser downloads, or document review workflows.
Exploitation context
The source bundle does not show CISA KEV listing or cite active exploitation. Exploitation requires user interaction: opening a malicious file or visiting a malicious page. Treat this as a credible phishing or document-delivery risk, not a remotely wormable service exposure.
Researcher notes
Evidence is strongest for affected product, version, impact, and bug class from CVE and ZDI-aligned text. The provided sources do not name a fixed version or detailed mitigation, so validation should center on version inventory and current Foxit bulletin guidance.
Mitigation direction
- Inventory endpoints for Foxit PDF Reader 11.0.0.49893.
- Check Foxit security bulletins for the vendor-fixed release and upgrade guidance.
- Limit risky PDF handling until affected installations are updated.
- Train users to avoid unexpected PDF files and links.
- Remove Foxit Reader where it is not required.
Validation and detection
- Confirm installed Foxit Reader versions through endpoint inventory or software management records.
- Verify affected systems no longer report version 11.0.0.49893 after remediation.
- Review email, web, and EDR alerts involving suspicious PDF files.
- Document exceptions and compensating controls for systems that cannot be upgraded.
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-416: 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-2021-34851 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
- 7.8 (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://www.foxit.com/support/security-bulletins.htmlCVE reference · x_refsource_MISC
- https://www.zerodayinitiative.com/advisories/ZDI-21-933/CVE 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.
Use After Free
Use After Free represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.