Vulnerability in Sumatrapdfreader Sumatrapdf
CVE-2026-25961
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.
Vulnerability class: Improper Certificate Validation
Published · last modified .
CVSS v3 metric
CVSS v3 base score 7.5 (High). Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:H.
EPSS exploit prediction
EPSS: 0.004 (35.7th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 36th percentile — 35.7% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.004 · newest: 0.004 · change: -0.000
Affected products
- Sumatrapdfreader Sumatrapdf — versions >= 3.5.0, <= 3.5.2
Weakness classification (CWE)
Public proof-of-concept exploits
References
- github.com/sumatrapdfreader/sumatrapdf/security/advisories/GHSA-xpm2-rr5m-x96q (Exploit, Vendor Advisory)
Frequently asked questions
- What is CVE-2026-25961?
- CVE-2026-25961 is a high-severity vulnerability in Sumatrapdfreader Sumatrapdf, classified under Improper Certificate Validation. CVSS score: 7.5/10. Published 2026-02-09.
- How severe is CVE-2026-25961?
- High severity. CVSS v3 base score is 7.5 out of 10.
- Is CVE-2026-25961 known to be exploited?
- 1 public proof-of-concept repositories are indexed. Not currently listed in the CISA KEV catalog.