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High · 7.5 Public exploit CVE-2026-25961 EUVD-2026-6869

SumatraPDF Update MITM -> Arbitrary Code Execution

Published Feb 9, 2026 · Updated Feb 10, 2026 · Assigned by GitHub_M

Vendor: sumatrapdfreader Product: sumatrapdf

Description

SumatraPDF is a multi-format reader for Windows. In 3.5.0 through 3.5.2, SumatraPDF's update mechanism disables TLS hostname verification (INTERNET_FLAG_IGNORE_CERT_CN_INVALID) and executes installers without signature checks. A network attacker with any valid TLS certificate (e.g., Let's Encrypt) can intercept the update check request, inject a malicious installer URL, and achieve arbitrary code execution.

Affected products

VendorProductAffectedFixed
sumatrapdfreader sumatrapdf >= 3.5.0, <= 3.5.2 —

Public exploits

Exploit or proof-of-concept code for this vulnerability is publicly available, which lowers the bar for attackers. Treat it as a reason to patch sooner.

Third-party code, not reviewed by us. Public PoCs are sometimes fake or contain malware. Read the code first and run it only in an isolated lab, against systems you are authorised to test.

Exploit-DB 1

GitHub 1 repository

  • mbanyamer/CVE-2026-25961-SumatraPDF-3.5.0---3.5.2-RCE ★ 2 · Feb 10, 2026

    SumatraPDF versions 3.5.0 to 3.5.2 disable TLS hostname verification during update checks # (using INTERNET_FLAG_IGNORE_CERT_CN_INVALID) and do not perform any signature or integrity # validation on …

Sources: PoC-in-GitHub, Metasploit Framework, Exploit-DB — updated daily. Only links are listed; no exploit code is hosted here.

References