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CVE-2026-25961

HIGHCVSS 7.5/10EPSS 0.45%

Last modified

CVE-2026-25961 is a high-severity vulnerability rated 7.5/10 on the CVSS scale. 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. EPSS estimates a 0.45% chance of exploitation in the next 30 days.

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.

Metrics

CVSS 3.1
7.5/10

CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:H

EPSS Probability
0.45%

35.6th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

Affected Software

VendorProductVersions
SumatrapdfreaderSumatrapdf>= 3.5, <= 3.5.2

References

Timeline

Published
Last Modified
Status
Analyzed

Frequently Asked Questions

What is 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.
How severe is CVE-2026-25961?
CVE-2026-25961 has a CVSS score of 7.5/10 (HIGH severity). The EPSS model estimates a 0.45% probability of exploitation in the next 30 days.
How do I fix CVE-2026-25961?
Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

Are you affected by CVE-2026-25961?

Run a free Strix scan to check your systems for this vulnerability.

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Source: NVD / NIST