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CVE-2026-25961— SumatraPDF Update MITM -> Arbitrary Code Execution

Quick assessment

Affected
sumatrapdfreader sumatrapdf
Exploitation
Public or AI PoC available; prioritize validation
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

sumatrapdf是sumatrapdfreader开源的一个PDF阅读器。 SumatraPDF 3.5.0版本至3.5.2版本存在安全漏洞，该漏洞源于更新机制禁用TLS主机名验证且不检查安装程序签名，可能导致任意代码执行。

CVSS 7.5 · High EPSS 0.48% · P40

Public Exploits 1

ExploitDB · 1 EDB-52535 [webapps]
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I. Basic Information for CVE-2026-25961

Vulnerability Information
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Vulnerability Title
SumatraPDF Update MITM -> Arbitrary Code Execution
Source: CVE Program / CVE List V5
Vulnerability 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.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:H
Source: CVE Program / CVE List V5
Vulnerability Type
证书验证不恰当
Source: CVE Program / CVE List V5
Vulnerability Title
sumatrapdf 安全漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
sumatrapdf是sumatrapdfreader开源的一个PDF阅读器。 SumatraPDF 3.5.0版本至3.5.2版本存在安全漏洞，该漏洞源于更新机制禁用TLS主机名验证且不检查安装程序签名，可能导致任意代码执行。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
sumatrapdfreader sumatrapdf >= 3.5.0, <= 3.5.2 -

II. Public POCs for CVE-2026-25961

# POC Description Source Link Shenlong Link
1 SumatraPDF 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. https://github.com/mbanyamer/CVE-2026-25961-SumatraPDF-3.5.0---3.5.2-RCE POC Details
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III. Intelligence Information for CVE-2026-25961

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Same Patch Batch · sumatrapdfreader · 2026-02-09 · 3 CVEs total

CVE-2026-25880 7.8 HIGH Untrusted Search Path in SumatraPDF Reader (explorer.exe on Windows)
CVE-2026-25920 5.5 MEDIUM SumatraPDF has a heap out-of-bounds read in MOBI HuffDic decompressor

IV. Related Vulnerabilities

Same product: sumatrapdf
Same vendor: sumatrapdfreader
Same weakness: CWE-295

V. Comments for CVE-2026-25961

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