SiYuan before 3.8.9 Nil Pointer Dereference DoS via MCP resources/read
- Exploited
- No known exploitation
- Fix
- Fixed in 3.8.9
- Who is exposed
- Not reported
Do first: Upgrade to a fixed version: 3.8.9.
- Last modified
- A 0-100 score for how much a CVE matters across the industry: exploitation, exposure, how widely the software is used, severity and whether a fix exists.What do these mean? →
- 10/100 · provisional
- Whether working attack code is public (Exploit-DB, Metasploit, Nuclei or GitHub). Public code makes attacks easier.What do these mean? →
- None on Exploit-DB, Metasploit or GitHub
Summary
SiYuan, a note-taking application, is affected by a denial-of-service flaw in its MCP resource handling that lets an attacker crash the kernel process and interrupt service. The attack can be launched over the network, but only by someone holding a valid API token, since the attacker needs high-level login access to send the request.
Written by anthropic/claude-haiku-5.5 from the sources below. Verify against them.
Read the original 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.
cve.now Index
- Exploitation?/40Unknown. No CISA SSVC exploitation rating yet
- Exposure3/25Reachable over the network · Unknown: No advisory context yet
- Reach?/20Unknown. No tracked technology or package matched
- Severity6.9/10CVSS 6.9
- No patch0/5No signal
What would change the score
- Would score about 65 if added to CISA KEV
- Would score about 60 if CISA's SSVC rates exploitation active
- Would score about 29 if advisories confirm default setups are exposed
What to do
Upgrade to a fixed version: 3.8.9.
Timeline
- CVE published
- First seen by cve.now
Affected versions
- siyuan-note siyuan
fixed in 3.8.9
Evidence 2
- Advisory
- Link
Corrections
None so far.
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Questions about CVE-2026-123492
Is CVE-2026-123492 being exploited?
It is not in CISA's Known Exploited Vulnerabilities catalog, and CISA's SSVC assessment does not mark exploitation as active. That does not mean it has not been attacked: vendors and researchers can report attacks before CISA lists them. No public exploit code is tracked.Source: cve.now feed data
Which versions are affected by CVE-2026-123492?
siyuan: before 3.8.9.Source: cve.now feed data
How do I fix CVE-2026-123492?
Upgrade to a fixed version: 3.8.9.Source: cve.now feed data