SiYuan WebSocket Authentication Bypass Exposes Protected Documents

SiYuan versions before v3.7.4 contain a publish-boundary bypass vulnerability in WebSocket broadcast sessions that allows anonymous readers to receive unfiltered edits. Attackers can establish a WebSocket connection to the publish surface and passively receive real-time content events including password-protected and forbidden documents without authentication.

Casky was already ahead

This CVE exploits attack patterns that Casky's 283matched skills already investigate — long before this vulnerability was disclosed. Claude's reasoning model maps these techniques to MITRE ATT&CK, so practitioners who ran these skills have already seen the threat behaviour in their findings.

Analysis

SiYuan versions prior to v3.7.4 suffer from a critical authentication bypass vulnerability in their WebSocket broadcast mechanism. Attackers can establish unauthenticated WebSocket connections to the publish surface and passively receive real-time content events, including modifications to password-protected and access-restricted documents. This vulnerability affects any organization or individual using vulnerable SiYuan instances for sensitive note-taking, knowledge management, or documentation—particularly those relying on access controls as a security boundary. The CVSS score of 8.6 reflects the severity: unauthorized information disclosure at scale without requiring active exploitation or user interaction.

Casky's 283 mapped skills leverage Claude's extended reasoning to detect the attack patterns underlying this CVE across MITRE ATT&CK techniques TA0004 (Privilege Escalation) and TA0006 (Credential Access). Practitioners using Casky would identify suspicious indicators such as unauthorized WebSocket session establishment without valid authentication tokens, anomalous real-time document access patterns from unauthenticated sources, and bulk retrieval of protected content metadata. The platform's skills specifically flag the disconnect between published-boundary enforcement and actual WebSocket filtering logic—detecting when broadcast sessions fail to validate access control lists before streaming sensitive edits. Security teams would see findings highlighting unencrypted transmission of protected document contents to unauthorized consumers and the absence of per-document authorization checks in the WebSocket handler, enabling them to prioritize patching and implement compensating controls like network segmentation or WebSocket traffic inspection.

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Casky Risk Score

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EPSS Probability

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Shodan Exposure

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GreyNoise Signal

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283 Casky skills cover this attack pattern

These skills use Claude AI's reasoning model to surface findings in the same attack categories as CVE-2026-72810.

abusing-dpapi-for-credential-access

red teaming · high

Run

abusing-shadow-credentials-for-privesc

red teaming · high

Run

Access with Stolen Session Cookie

cryptography · low

Run

MITRE ATT&CK Techniques

TA0004 TA0006

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Casky has 283 skills that investigate the attack patterns behind CVE-2026-72810. Run one and get CVSS-scored findings in 3 minutes.

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