High severity7.5NVD Advisory· Published Feb 9, 2026· Updated Jun 17, 2026
CVE-2026-25961
CVE-2026-25961
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.
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Affected products
3cpe:2.3:a:sumatrapdfreader:sumatrapdf:*:*:*:*:*:*:*:*+ 2 more
- cpe:2.3:a:sumatrapdfreader:sumatrapdf:*:*:*:*:*:*:*:*range: >=3.5,<=3.5.2
- (no CPE)range: 3.5.0-3.5.2
- (no CPE)range: >= 3.5.0, <= 3.5.2
Patches
Vulnerability mechanics
References
1- github.com/sumatrapdfreader/sumatrapdf/security/advisories/GHSA-xpm2-rr5m-x96qnvdExploitVendor Advisory
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