Security readout for executives and security teams
Plain-English summary
Foxit Reader 10.1.4.37651 can be compromised when a user opens a malicious PDF. The bug is in the JavaScript engine and can allow attacker-controlled code to run. This is high risk for endpoints where Foxit handles untrusted PDFs.
Executive priority
Treat this as a prioritized endpoint remediation issue where Foxit Reader processes external documents. User interaction is required, but malicious PDFs are a realistic delivery path and successful exploitation could compromise confidentiality, integrity, and availability.
Technical view
CVE-2021-21870 is a CWE-416 use-after-free in Foxit Reader’s JavaScript engine. A specially crafted PDF can trigger reuse of freed memory and lead to arbitrary code execution. The CVSS 3.0 score is 8.8, with network attack vector and required user interaction.
Likely exposure
Exposure is most likely on desktops using Foxit Reader 10.1.4.37651, especially where users receive external PDFs. Browser-based exposure is possible if the Foxit browser plugin extension is enabled.
Exploitation context
The source bundle does not show CISA KEV listing or active exploitation evidence. Exploitation requires convincing a user to open a malicious PDF or visit a malicious site when the browser plugin extension is enabled.
Researcher notes
The public details identify the vulnerable component and impact but do not provide patch details in the supplied bundle. Avoid assuming other Foxit products or versions are affected unless vendor guidance confirms them.
Mitigation direction
- Identify systems running Foxit Reader 10.1.4.37651.
- Check Foxit guidance for fixed versions or vendor-supported remediation.
- Update or replace affected Foxit Reader installations where guidance confirms a fix.
- Disable the Foxit browser plugin extension where not required.
- Harden email and web controls for untrusted PDF attachments.
Validation and detection
- Inventory endpoint software versions for Foxit Reader 10.1.4.37651.
- Confirm whether the Foxit browser plugin extension is enabled.
- Review mail, web, and EDR telemetry for suspicious PDF delivery or execution.
- Verify remediated systems no longer run the affected version.
- Document compensating controls for systems that cannot be updated.
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-2021-21870 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
- 8.8 (3.0)
- Known Exploited
- No
- Published
Vector: CVSS:3.0/AV:N/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:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H2.85.9Primary CVE scoreVulnerability scoring details
Base CVSS 3.0 score
8.8HighVector: CVSS:3.0/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
Source materials
- CVE List V5 sourceCVE List V5
- https://talosintelligence.com/vulnerability_reports/TALOS-2021-1307CVE 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.