Security readout for executives and security teams
Plain-English summary
A malicious PDF or web page could make Foxit PDF Editor run attacker-controlled code if a user opens it. The issue is a memory safety bug in square annotation handling. Business risk is workstation compromise, not server-side exposure, and the provided sources do not show active exploitation or CISA KEV listing.
Executive priority
Treat this as a high-priority endpoint remediation item for users who handle external PDFs. It requires user interaction, but successful exploitation could compromise the user’s workstation. Prioritize inventory, vendor update confirmation, and patch deployment over emergency incident assumptions.
Technical view
CVE-2021-34959 is a CWE-416 use-after-free in Foxit PDF Editor annotation object handling. The flaw involves operating on an object without validating that it still exists. ZDI states an attacker could execute code in the current process after user interaction. The listed affected version is Foxit PDF Editor 11.0.0.49893.
Likely exposure
Exposure is most likely on endpoints where Foxit PDF Editor 11.0.0.49893 is installed and users open untrusted PDFs or visit attacker-controlled pages. The bundle does not establish exposure for other Foxit products or versions.
Exploitation context
User interaction is required: the target must open a malicious file or visit a malicious page. The CVSS score is 7.8 with high confidentiality, integrity, and availability impact. The bundle marks KEV as false and provides no cited evidence of active exploitation.
Researcher notes
The source bundle identifies the vulnerable component as Square Annotation handling and attributes the root cause to missing object-existence validation. Evidence is enough to guide detection by installed version and affected workflow, but it does not provide patch details, broader version ranges, or confirmed exploitation status.
Mitigation direction
- Inventory endpoints for Foxit PDF Editor, especially version 11.0.0.49893.
- Check Foxit security bulletins for the vendor-designated fixed version or mitigation.
- Prioritize updating affected endpoints after vendor guidance is confirmed.
- Limit opening of unsolicited PDFs from email, web downloads, and external portals.
- Use endpoint controls to contain PDF reader processes where available.
Validation and detection
- Confirm whether Foxit PDF Editor 11.0.0.49893 exists in software inventory.
- Verify installed Foxit versions against Foxit security bulletin guidance.
- Confirm updated endpoints no longer report the affected version.
- Review endpoint alerts for suspicious Foxit PDF Editor crashes or child processes.
- Document any compensating controls for endpoints awaiting remediation.
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-2021-34959 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
- ZDI-21-1190CVE reference · x_research-advisory
- vendor-provided URLCVE reference · vendor-advisory
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.