CVE-2026-25961 — Improper Certificate Validation in Sumatrapdf
Severity
7.5HIGHNVD
EPSS
0.0%
top 94.21%
CISA KEV
Not in KEV
Exploit
No known exploits
Affected products
Timeline
PublishedFeb 9
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.
CVSS vector
CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:HExploitability: 1.6 | Impact: 5.9