Is CVE-2026-123492 exploited in the wild?

No. Junglewise Threat Intelligence has no report of CVE-2026-123492 being exploited in the wild.

How severe is CVE-2026-123492?

Medium severity, with a CVSS score of 4.9, published 6 November 2026.

Is there a fix for CVE-2026-123492?

Yes: fixed in 3.8.9. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

How is CVE-2026-123492 attacked?

It is attacked over the network, in a hosted service.

Am I affected by CVE-2026-123492?

Check whether you run B3log Siyuan at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

CVE-2026-123492: SiYuan nil pointer dereference in MCP privateCacheMiddleware

CVE-2026-123492 · Severity: medium · CVSS 4.9 · Published 2026-11-06

SiYuan is a note-taking application with an embedded kernel that supports the Model Context Protocol (MCP) for external integrations. An authenticated attacker with a valid API token can crash the kernel by sending a resources/read request for a nonexistent resource, causing service interruption and potential data loss if unsaved edits exist.

Technologies: B3log Siyuan. Vendors: B3log.

Quick answers

Is CVE-2026-123492 exploited in the wild?: No. Junglewise Threat Intelligence has no report of CVE-2026-123492 being exploited in the wild.
How severe is CVE-2026-123492?: Medium severity, with a CVSS score of 4.9, published 6 November 2026.
Which products and versions are affected?: B3log Siyuan before 3.8.9.
Is there a fix for CVE-2026-123492?: Yes: fixed in 3.8.9. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
How is CVE-2026-123492 attacked?: It is attacked over the network, in a hosted service.
Am I affected by CVE-2026-123492?: Check whether you run B3log Siyuan at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

How to fix

Fixed in: 3.8.9

Technical details

The privateCacheMiddleware in kernel/mcp/server.go performs an unchecked type switch on MCP result pointers and dereferences them without verifying they are non-nil. When resources/read is called with an unregistered URI, go-sdk v1.8.0 returns a typed nil pointer (*ReadResourceResult) with an error; the middleware then dereferences this nil pointer in the case branch, triggering a panic that crashes the kernel process.

Affected products

b3log SiYuan before 3.8.9

Timeline

2026-10-22: disclosed
2026-11-06: advisory

References

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