CVE-2026-25961 – SumatraPDF Update MITM -> Arbitrary Code Execution

CVE ID : CVE-2026-25961

Published : Feb. 9, 2026, 9:34 p.m. | 47 minutes ago

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.

Severity: 0.0 | NA

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