CVE-2025-55309: 
Foxit PDF Reader vulnerability analysis and mitigation

CVE-2025-55309 is a use-after-free vulnerability in Foxit PDF Reader and PDF Editor for Windows and macOS. A crafted PDF containing JavaScript that attaches an OnBlur action on a form field can trigger premature release of an annotation object during user right-click interaction, resulting in memory corruption or application crashes. Affected versions include Foxit PDF Editor and Reader before 13.2 and 2025 before 2025.2. It carries a CVSS v3.1 base score of 6.7 (Medium) (Foxit Security Bulletins, Red Hat CVE).

The vulnerability is classified as CWE-416 (Use After Free). A malicious PDF embeds JavaScript that registers an OnBlur event handler on a form field; this handler destroys an annotation object. When the user right-clicks on the form field, Foxit's internal focus-change handling triggers the OnBlur action, which frees the annotation object. The program then continues to reference the freed memory, leading to a use-after-free condition that can corrupt memory or crash the application (Foxit Security Bulletins, Red Hat CVE). Exploitation requires the attacker to deliver a crafted PDF to a target user and requires the user to perform a right-click interaction on the affected form field.

Successful exploitation can result in memory corruption or application crashes, potentially enabling denial of service. Depending on how the memory corruption is leveraged, there is a possibility of arbitrary code execution in the context of the user running Foxit PDF Reader or Editor. Confidentiality, integrity, and availability are all rated as HIGH impact in the CVSS scoring, though the attack complexity is high and user interaction is required (Foxit Security Bulletins, Red Hat CVE).

1. Craft malicious PDF: Create a PDF document containing a form field with embedded JavaScript that registers an OnBlur event handler. The handler is designed to destroy (free) the annotation object associated with the form field.
2. Deliver the PDF: Send the crafted PDF to the target user via email, file share, or web download, social-engineering them into opening it with a vulnerable version of Foxit PDF Reader or Editor (before 13.2 or before 2025.2).
3. Trigger user interaction: Wait for the user to right-click on the affected form field within the PDF. This triggers Foxit's internal focus-change handling, which fires the OnBlur event.
4. Trigger use-after-free: The OnBlur JavaScript destroys the annotation object; Foxit's focus-change code then attempts to access the already-freed annotation object, causing a use-after-free condition.
5. Achieve impact: Depending on memory layout and exploitation sophistication, the result may be an application crash (denial of service) or, in advanced scenarios, controlled memory corruption enabling code execution in the context of the user (Foxit Security Bulletins).

• File System: Presence of unexpected or suspicious PDF files with embedded JavaScript, particularly those containing OnBlur event handlers on form fields.
• Process: Foxit PDF Reader or Editor process crashing unexpectedly (application crash dumps) after a user right-clicks on a PDF form field.
• Logs: Application crash logs or Windows Error Reporting entries referencing Foxit PDF Reader/Editor processes with access violation or heap corruption errors.
• Network: Unusual outbound network connections from the Foxit process following a crash or unexpected behavior, which could indicate post-exploitation activity if code execution is achieved.

Foxit has released patched versions addressing this vulnerability: upgrade Foxit PDF Editor and PDF Reader to version 13.2 or later, or 2025.2 or later (Foxit Security Bulletins). As a temporary workaround, disable JavaScript execution in Foxit PDF Reader/Editor via application settings to prevent the malicious OnBlur handler from executing. Users should avoid opening PDF files from untrusted sources and exercise caution with right-click interactions on form fields in PDFs of unknown origin. Application whitelisting and restricting PDF processing to trusted files can further reduce risk.

The vulnerability was noted by Tenable's plugin pipeline and referenced in patch management catalogs such as Patch My PC's August 2025 update catalog (Patch My PC). No significant public researcher commentary or media coverage has been identified beyond standard vulnerability tracking and advisory aggregation.