CVE-2026-25961Public exploitNetwork attack vector

Code execution via unverified update installer

Published Feb 9, 2026 · Updated Feb 9, 2026

Improper certificate validation in SumatraPDF 3.5.0 through 3.5.2 allows man-in-the-middle attackers to execute code via updates. HttpGet() disables TLS hostname matching, while UpdateCheck accepts an unrestricted download URL and launches the retrieved installer without a signature or hash check. Exploitation requires a network interception position, a certificate from a trusted authority, and a user click on the legitimate-looking Install prompt; the payload runs as the current user.

CVSS severity7.5
High
EPSS probability0.45%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Improper certificate validation in SumatraPDF 3.5.0 through 3.5.2 allows man-in-the-middle attackers to execute code via updates. HttpGet() disables TLS hostname matching, while UpdateCheck accepts an unrestricted download URL and launches the retrieved installer without a signature or hash check. Exploitation requires a network interception position, a certificate from a trusted authority, and a user click on the legitimate-looking Install prompt; the payload runs as the current user.

The record

CVE
CVE-2026-25961
Published
Feb 9, 2026
Updated
Feb 9, 2026
Vendor
SumatraPDF
Product
SumatraPDF
Classifications
CWE-494, CWE-295, T1204.002, T1557
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Feb 9, 2026CVE publishedPublication date reported by the CVE source.
  2. Feb 9, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=>= 3.5.0, <= 3.5.2

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

SumatraPDF · SumatraPDFversion=>= 3.5.0, <= 3.5.2

Published CVSS scores

7.5GitHubCVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-494Download of Code Without Integrity Check
CWE-295Improper Certificate Validation
T1204.002Malicious File
T1557Adversary-in-the-Middle

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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