Security readout for executives and security teams
Plain-English summary
CVE-2021-34839 is a Foxit PDF Reader flaw that can let an attacker run code when a user opens a malicious PDF or visits a malicious page. It is not described as remotely exploitable without user interaction. The main business risk is phishing-led compromise of workstations running the affected Foxit version.
Executive priority
Treat as high priority for workstation patching, especially where staff receive external documents. It is serious because successful exploitation can run attacker code, but urgency is moderated by required user interaction and lack of KEV evidence in the bundle.
Technical view
The flaw affects Foxit PDF Reader 11.0.0.49893. It occurs in Annotation object handling and involves operating on an object without validating that it exists. The CVE maps to CWE-416 and can lead to arbitrary code execution in the current process context after user interaction.
Likely exposure
Exposure is limited to systems with Foxit PDF Reader 11.0.0.49893 installed, especially endpoints where users open externally supplied PDFs or browse untrusted content. The source bundle does not identify other Foxit products or versions as affected.
Exploitation context
The source bundle says exploitation requires user interaction: opening a malicious file or visiting a malicious page. It is not listed as KEV, and the provided sources do not state active exploitation in the wild.
Researcher notes
ZDI identifies this as ZDI-CAN-14020. The vulnerable area is Annotation object handling, with missing existence validation before object operations. Keep validation focused on version exposure and vendor advisory alignment; the provided bundle does not include exploit indicators or fixed-version specifics.
Mitigation direction
- Inventory endpoints for Foxit PDF Reader 11.0.0.49893.
- Check Foxit security bulletins for the vendor-approved fixed release.
- Update or remove affected Foxit PDF Reader installations.
- Reduce exposure to untrusted PDFs until remediation is complete.
- Use email and web controls to limit malicious PDF delivery.
Validation and detection
- Confirm installed Foxit PDF Reader versions across managed endpoints.
- Verify no production endpoint remains on version 11.0.0.49893.
- Review Foxit advisory details before marking remediation complete.
- Check security telemetry for suspicious Foxit process behavior.
- Confirm PDF handling policies for high-risk user groups.
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-2021-34839 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-21-921/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.