CVE-2026-100642

SiYuan v2.1.0 before v3.8.4 Cross-Site Request Forgery via CheckAuth

HIGH
7.6
CVSS Score
Published: September 26, 2026 at 01:23 PM UTC
Updated: September 30, 2026 at 03:17 PM UTC
2 products affected across 2 vendorsSiyuanSiyuan

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Severity
HIGH7.6
Exploit prediction
EPSS 0.1%
SSVC
PoC

Description

SiYuan versions from v2.1.0 before v3.8.4 contain a cross-site request forgery vulnerability in the CheckAuth lock-screen pass-through branch that grants administrator access to loopback requests without validating Origin headers. Attackers can craft malicious web pages that force victims to terminate the kernel process, read workspace configuration and proxy settings, and trigger administrative actions via zero-credential cross-origin requests from the victim's browser.

Affected

Our own answer: ranges merged, affected separated from platform-only, with confidence and review flags.

2.1.0 ≤ v < 3.8.4
Affected range stops below 3.8.4, so it looks safe — our inference, not a vendor statement
2.1.0 ≤ v < 3.8.42.1.0
Vendor states this is fixed in 3.8.4 (unaffected)

Remediation

No guide yet

No remediation guidance has been written for this CVE yet. What the record does show:

SSVC — Action Prioritization

SSVCPoCNot automatablePartial impact

SSVC signals action urgency (what to patch first), separate from CVSS which measures severity.

CVSS

7.6HIGHVulnCheck
Attack Vector
NETWORK
Complexity
LOW
Privileges
NONE
User Interaction
REQUIRED
Scope
UNCHANGED
Confidentiality
LOW
Integrity
LOW
Availability
HIGH
Vector?

Quick Info

StatusDEFERRED
CWE
CWE-346

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