Windows
CVE-2026-25961
HIGH
Severity by source
AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:H
Primary rating from GitHub Advisory · only source for this CVE.
CVSS VectorGitHub Advisory
CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:H
Lifecycle Timeline
3DescriptionGitHub Advisory
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.
AnalysisAI
SumatraPDF versions 3.5.0 through 3.5.2 fail to validate TLS certificates during software updates and execute installers without signature verification, allowing network attackers to perform man-in-the-middle attacks and inject malicious code. An attacker with any valid TLS certificate can intercept update requests and redirect users to a malicious installer, achieving arbitrary code execution on Windows systems. …
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Attack ChainAIDerived
Hypothetical attack flow derived from CVE metadata
Vulnerability AssessmentAI
| Exploitation | SumatraPDF versions 3.5.0–3.5.2 with active update mechanism enabled. … Additional conditions and limiting factors are described in the full assessment. |
| Risk Assessment | CVSS 7.5 (HIGH). … Full risk analysis with EPSS, KEV, and SSVC signal comparison available after sign-in. |
| Exploit Scenario | A remote attacker could exploit this vulnerability to compromise the affected system. |
| Remediation | Monitor vendor advisories for a patch. … Detailed patch versions, workarounds, and compensating controls in full report. |
Recommended ActionAI
Within 24 hours: Inventory all SumatraPDF installations across the organization and identify affected versions (3.5.0-3.5.2). …
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External POC / Exploit Code
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