Description

Foxit PDF Reader versions earlier than 2026.2 are affected by CVE-2026-57239, a recently disclosed local privilege escalation vulnerability discovered by security researcher Luke Paris. The flaw allows an attacker who already has code execution as a low-privileged Windows user to elevate privileges to NT AUTHORITY\SYSTEM. The issue exists because FoxitPDFReaderUpdateService.exe, which runs with SYSTEM privileges, processes a user-writable FoxitData.txt file stored in the ProgramData directory. Since standard users can modify this file, attackers can abuse the updater workflow to trigger privileged operations. The attack involves supplying a crafted encrypted request through FoxitData.txt, which uses AES encryption with a hard-coded key and UTF-16 little-endian encoding. This request instructs the privileged service to execute FoxitPDFReaderUpdater.exe from the user’s AppData directory. Although Foxit validates updater binaries and digital signatures, the researcher demonstrated a DLL sideloading technique by placing a malicious winspool.drv file in the updater’s working directory. When the updater displays a graphical update prompt, the malicious module is loaded, allowing arbitrary code execution through its DllMain function with SYSTEM privileges. Successful exploitation can facilitate credential theft, security tool evasion, persistence, and further post-compromise activity. Foxit has fixed the vulnerability in Foxit PDF Reader 2026.2, and users should upgrade immediately. Security teams should monitor for unauthorized modifications to FoxitData.txt and investigate suspicious .dll or .drv files within %APPDATA%\Foxit\Software\Continuous\Addon\Foxit\PDF\Reader. Additional detection measures include monitoring Windows Event ID 4688 for unusual process creation and token-related activity. Organizations can further reduce risk by enforcing application control policies through AppLocker or Windows Defender Application Control (WDAC) to block unauthorized DLL loading and execution.