High advisory for SumatraPDF

Advisory overview

SumatraPDF is a multi-format reader for Windows. In version 3.6.1 and earlier, HttpGet() in src/base/Http_win.cpp unconditionally passes INTERNET_FLAG_IGNORE_CERT_CN_INVALID to WinINet, disabling hostname matching for HTTPS update metadata and crash-symbol requests while retaining certificate-chain validation. A network-positioned attacker with a Windows-trusted certificate for an attacker-controlled domain can impersonate the project's update host, inject promo text and a clickable URL before update metadata validation, and provide an attacker-controlled archive to ExtractSymbols(). Installer replacement is not directly possible because HttpGetToFile() validates TLS and MaybeStartUpdateDownload() restricts the download host. No fixed version is available as of this review.

Related references

• https://github.com/sumatrapdfreader/sumatrapdf/commit/bd30134175e897dd5ed0d7fd14acce52eeca7183
• https://github.com/sumatrapdfreader/sumatrapdf/security/advisories/GHSA-mjwr-9w29-jp96