CVE-2026-25961
SumatraPDF Update MITM -> Arbitrary Code Execution
- Published
- Feb 9, 2026
- Updated
- Feb 10, 2026
- Assigning CNA
- GitHub_M
- Evidence observed
- Apr 30, 2026
Primary CVSS
nvd · CVSS 3.1
CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:HLow · next 30 days
- Percentile
- 38.6%
- Model date
- Sep 21, 2026
EPSS is a statistical estimate, not a certainty or a measure of impact. Combine it with CVSS, KEV status, exposure and your environment.
Summary
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.
Sources
2SumatraPDF versions 3.5.0 to 3.5.2 disable TLS hostname verification during update checks # (using INTERNET_FLAG_IGNORE_CERT_CN_INVALID) and do not perform any signature or integrity # validation on the downloaded installer.
banyamer · multiple · Apr 30, 2026
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