CVE-2026-123492— SiYuan before 3.8.9 Nil Pointer Dereference DoS via MCP resources/read

Quick assessment

Affected

siyuan-note siyuan

Exploitation

No confirmed in-the-wild exploitation; assess based on exposure

Recommended action

Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

SiYuan 在 3.8.9 版本之前存在一个空指针解引用漏洞，该漏洞位于组件中。已认证的攻击者可以通过读取不存在的 MCP 资源，触发内核崩溃。拥有有效 API 令牌的攻击者可在已初始化的 MCP 会话中发送请求，从而引发恐慌（panic），导致内核进程终止并中断服务。

CVSS 4.9 · Medium Updated Nov 06, 2026

Possible ATT&CK Techniques 1 AI

T1190 · Exploit Public-Facing Application

Affected Version Matrix 2

Vendor	Product	Version Range	Status
siyuan-note	siyuan	`< 3.8.9`	affected
		`3.8.9`	unaffected

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Vulnerability Information

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Vulnerability Title

SiYuan before 3.8.9 Nil Pointer Dereference DoS via MCP resources/read

Source: CVE Program / CVE List V5

Vulnerability Description

SiYuan before 3.8.9 contains a nil pointer dereference vulnerability in privateCacheMiddleware that allows authenticated attackers to crash the kernel by reading nonexistent MCP resources. Attackers with a valid API token can send a resources/read request in an initialized MCP session, causing a panic that terminates the kernel process and interrupts service.

Source: CVE Program / CVE List V5

CVSS Information

CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:H

Source: CVE Program / CVE List V5

Vulnerability Type

空指针解引用

Source: CVE Program / CVE List V5

Affected Products

Vendor	Product	Affected Versions	CPE	Subscribe
siyuan-note	siyuan	0 ~ 3.8.9	-

II. Public POCs for CVE-2026-123492

#	POC Description	Source Link	Shenlong Link

AI-Generated POC Premium

No public POC found.

III. Intelligence Information for CVE-2026-123492

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Other References for CVE-2026-123492 (2)

https://github.com/siyuan-note/siyuan/security/advisories/GHSA-2x3p-x74g-442x vendor-advisory
https://www.vulncheck.com/advisories/siyuan-before-3.8.9-nil-pointer-dereference-dos-via-mcp-resources-read third-party-advisory

https://www.cve.org/CVERecord?id=CVE-2026-123492

IV. Related Vulnerabilities

Same product: siyuan

Same vendor: siyuan-note

Same weakness: CWE-476