Bug 2567910 (CVE-2026-115758)

Summary: CVE-2026-115758 sumatrapdf: SumatraPDF: Update host impersonation via disabled TLS hostname validation
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerability-draftAssignee: Product Security DevOps Team <prodsec-dev>
Status: NEW --- QA Contact:
Severity: medium Docs Contact:
Priority: medium    
Version: unspecifiedKeywords: Security
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Hardware: All   
OS: Linux   
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A flaw was found in SumatraPDF. The application fails to validate the hostname on security certificates when making encrypted Hypertext Transfer Protocol Secure (HTTPS) connections for update checks and crash reports. A network-positioned attacker with a trusted certificate for an attacker-controlled domain can exploit this issue to impersonate the update servers. Successful exploitation allows the attacker to inject arbitrary content, spoof update metadata, and deliver untrusted archives to the client.
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Description OSIDB Bzimport 2026-11-05 22:35:41 UTC 
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.