CVE-2026-74868 in SiYuan
Summary
by MITRE • 08/17/2026
SiYuan versions before 3.7.4 contain an unthrottled brute-force vulnerability in the Publish Service Basic Auth implementation (PublishServiceTransport.RoundTrip() in kernel/server/proxy/publish.go). The Publish Service runs on a separate, unauthenticated-by-default listener (default TCP port 6808) and gates named publish-viewer accounts (Conf.Publish.Auth.Accounts) with Basic Auth that has no rate limiting, per-account lockout, or backoff. Unauthenticated remote attackers can submit unlimited password guesses against named accounts to gain access to published notes/notebooks.
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Analysis
by VulDB Data Team • 08/17/2026
The vulnerability identified in SiYuan versions prior to 3.7.4 represents a critical authentication bypass risk stemming from the absence of rate limiting mechanisms within the Publish Service's Basic Authentication implementation. This service operates on a dedicated network listener, typically bound to TCP port 6808 by default, which is designed to expose specific published notes and notebooks to external users without requiring full application login credentials for general access. However, when accessing these resources via named publish-viewer accounts, the system relies solely on HTTP Basic Authentication headers. The core technical flaw lies in the implementation of PublishServiceTransport.RoundTrip within the kernel/server/proxy/publish.go module, which fails to enforce any throttling controls, account lockout policies, or exponential backoff strategies against repeated authentication failures. This architectural oversight allows an unauthenticated remote attacker to interact with the service without restriction, effectively creating a high-speed brute-force attack vector that can be exploited from anywhere on the internet if the port is exposed.
From a technical perspective, this vulnerability aligns directly with CWE-307 Improper Restriction of Excessive Authentication Attempts and CWE-287 Improper Authentication. The lack of rate limiting means that an attacker can utilize automated tools to submit thousands or millions of password guesses per minute against targeted account names. Since the service does not implement per-account lockouts, there is no mechanism to temporarily disable a target after a threshold of failed attempts, nor are there delays introduced between requests to slow down offline cracking efforts. This allows attackers to perform rapid credential stuffing attacks using common username and password dictionaries or previously leaked credentials from other breaches. The vulnerability is particularly severe because the Publish Service often contains sensitive user data that has been explicitly shared for public or semi-public consumption, making it a high-value target for unauthorized access.
The operational impact of this flaw extends beyond simple account compromise to potential data exfiltration and privacy violations. Successful exploitation allows an attacker to gain read-only access to all published notes and notebooks associated with the compromised publish-viewer accounts. Depending on the configuration, these accounts may have permissions that allow viewing sensitive personal information, proprietary business documents, or intellectual property that was intended for a limited audience but is now accessible due to weak authentication controls. Furthermore, because Basic Authentication transmits credentials in base64 encoding rather than true encryption, if this service is accessed over an unencrypted HTTP connection, the credentials are transmitted in cleartext, further facilitating interception and replay attacks by network-level adversaries. This scenario also maps to MITRE ATT&CK technique T1110 Brute Force, specifically highlighting how insufficient monitoring and control of authentication events can lead to successful unauthorized access.
To mitigate this vulnerability, organizations running SiYuan must upgrade immediately to version 3.7.4 or later where these rate-limiting controls have been implemented by the developers. For environments that cannot yet upgrade, immediate remediation steps include restricting network-level access to TCP port 6808 using firewall rules so that only trusted IP addresses can reach the Publish Service. Additionally, administrators should ensure that HTTPS is enforced for all connections to this service to prevent credential interception via man-in-the-middle attacks. It is also advisable to review the list of publish-viewer accounts and remove any unnecessary entries or those with weak passwords, ensuring that strong, unique credentials are used for each account. Implementing a reverse proxy in front of SiYuan can further enhance security by adding external rate-limiting capabilities using tools like Nginx or Apache before requests even reach the application layer, providing an additional defense-in-depth measure against brute-force attempts.