CVE-2026-57256: Foxit PDF Reader Use-After-Free Denial of Service

Technical summary

CVE-2026-57256 is a use-after-free vulnerability (CWE-416) in Foxit PDF Editor and Foxit PDF Reader affecting both Windows and macOS platforms. The flaw occurs during PDF rendering when JavaScript execution triggers abnormal operations on list box form fields. After form reset operations, the application fails to validate form object integrity and correctly manage internal dictionary pointers. This results in dereferenced invalid memory addresses, causing a denial of service via application crash. The vulnerability requires local file access and user interaction to trigger.

Business impact

Organizations relying on Foxit products for PDF review and processing workflows face service disruption risk. If users regularly open PDFs from untrusted sources—such as customer submissions, email attachments, or public repositories—attackers can cause repeated crashes, degrading productivity and potentially disrupting document processing pipelines. While the impact is limited to availability (denial of service), the ease of exploitation and prevalence of Foxit in enterprise document workflows warrant prompt remediation.

Affected systems

Foxit PDF Editor and Foxit PDF Reader on Windows and macOS operating systems are affected. The vulnerability is triggered during PDF parsing and JavaScript execution, affecting all versions until a patch is released. No vendor patch information has been provided; organizations should consult Foxit's official advisories for specific affected version ranges and remediation timelines.

Exploitability

Exploitation requires minimal complexity: an attacker crafts a PDF containing malicious JavaScript and form field operations, then delivers it to a user (via email, website, or file sharing). When the user opens the PDF in a vulnerable Foxit application, the malformed form operations trigger the crash. No authentication, elevated privileges, or network access is required. The user interaction requirement (opening the file) is a moderate barrier, but social engineering can overcome it in targeted scenarios.

Remediation

Update Foxit PDF Editor and Foxit PDF Reader to patched versions as released by Foxit. Until patches are available, mitigate risk by implementing email gateway controls to block suspicious PDFs, educating users to avoid opening unexpected PDF attachments, and restricting JavaScript execution in PDF readers where operationally feasible. Consider disabling form-based features if they are not essential to your workflow.

Patch guidance

Monitor Foxit's official security advisories and release notes for updates addressing CVE-2026-57256. Once patches are released, prioritize deployment across all affected Foxit installations. Verify patching by checking application version strings or using Foxit's patch verification tools. Test patches in a controlled environment before enterprise rollout to ensure compatibility with existing PDF workflows and macros.

Detection guidance

Monitor for repeated Foxit application crashes when users open PDFs from external sources. Endpoint Detection and Response (EDR) tools can flag abnormal process termination patterns tied to PDF file operations. Review email logs for suspicious PDF attachments, particularly those with embedded JavaScript or complex form structures. Consider deploying file sandboxing to safely detonate suspicious PDFs before user delivery. Network monitors may detect unusual PDF file transfers if they exhibit characteristics of weaponized samples.

Why prioritize this

Despite a CVSS score of 7.8 (HIGH), this vulnerability presents moderate practical urgency. The attack surface is broad (all Foxit users) and user interaction is readily achievable through social engineering. However, impact is limited to denial of service rather than data theft or code execution. Prioritize patching for endpoints in high-risk roles (legal, finance, compliance teams) who regularly process external PDFs, and for users in targeted industries or organizations. Standard endpoints can be patched on the next maintenance window.

Risk score, explained

The CVSS 3.1 score of 7.8 reflects a HIGH severity vulnerability with low attack complexity and no privilege requirements. The vector (AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H) indicates local attack vector, but realistic delivery via malicious PDF attachment achieves this. While confidentiality, integrity, and availability impacts are scored as HIGH in the vector, actual exploitability is constrained to denial of service (application crash). The score appropriately flags this as a significant risk requiring prompt remediation, though not an emergency equal to remote code execution vulnerabilities.

Frequently asked questions