CVE
SiYuan 3.7.0 before 3.8.10 Path Traversal File Write via MCP web_fetch
- Exploited
- No known exploitation
- Fix
- Fixed in 3.8.10
- Who is exposed
- Not reported
Do first: Upgrade to a fixed version: 3.8.10.
- Published
- Last modified
- Whether it needs action now or is a reference record, by fixed rules, with why. Last checked is when cve.now last re-read it.What do these mean? →
- Reference
- Last checked
- 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? →
- 13/100 · 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
SiyuanNote's SiYuan app, on Windows, can be made to write files outside its import folder when it fetches a crafted URL through the MCP web_fetch or http_request tools. An attacker can reach it remotely without logging in, but the victim has to take an action, and the attacker can only write to folders the SiYuan user is able to modify.
Written by anthropic/claude-haiku-5.5 from the sources below. Verify against them.
Read the original description
SiYuan 3.7.0 before 3.8.10 on Windows contains a path traversal vulnerability in kernel/util/webfetch.go that allows attackers to write files outside the import directory via backslash-encoded filenames. Attackers controlling a URL fetched by the MCP web_fetch or http_request tools can use %5C-encoded ..\ sequences to write chosen response bytes to directories above temp/import that are writable by the SiYuan user.
cve.now Index
- Exploitation?/40Unknown. No CISA SSVC exploitation rating yet
- Exposure7/25Reachable over the network without a login · Unknown: No advisory context yet
- Reach?/20Unknown. No tracked technology or package matched
- Severity6/10CVSS 6.0
- No patch0/5No signal
What would change the score
- Would score about 68 if added to CISA KEV
- Would score about 63 if CISA's SSVC rates exploitation active
- Would score about 28 if advisories confirm default setups are exposed
What to do
Upgrade to a fixed version: 3.8.10.
Check your systems with an agent
Paste this into a coding or ops agent. It checks your systems read-only and reports a table per asset.
Check whether my systems are affected by CVE-2026-126776 (SiYuan 3.7.0 before 3.8.10 Path Traversal File Write via MCP web_fetch), using the cve.now data below.
Rules: work read-only. Do not run exploit code, proof-of-concept scripts or scanners that send attack payloads, and do not change any configuration, package, image or deployment. Report findings only.
What cve.now has for CVE-2026-126776 (entry last updated 2026-11-11):
Affected:
- siyuan-note siyuan: from 3.7.0, fixed in 3.8.10
Fixed versions: 3.8.10.
Setup: unknown whether the bug needs a non-default feature or setting. Check the advisory.
CISA KEV: CVE-2026-126776 is not listed as of cve.now's last read.
This KEV status is for CVE-2026-126776 only. If you also check another CVE, look up its own KEV status; never assume it from this one.
How to check:
- Installed software: check what is actually running, not what a repo declares. Read the version from each host, container image and Kubernetes node (the binary's version output, the OS package database, image layers), and check whether the conditions above hold there. Distribution packages may carry a backported fix under an older version number; confirm against the distribution's own advisory.
Verify against the linked advisories before concluding, and cite the date you read each one:
- https://github.com/siyuan-note/siyuan/security/advisories/GHSA-hq2c-hh95-vrr6
- https://github.com/siyuan-note/siyuan/commit/94d6a42a0362c0a6938a29ab84addb1fe0aca21c
- https://github.com/siyuan-note/siyuan/releases/tag/v3.8.10
- https://github.com/siyuan-note/siyuan/blob/v3.7.0/kernel/util/webfetch.go#L155
- https://www.vulncheck.com/advisories/siyuan-3.7.0-before-3.8.10-path-traversal-file-write-via-mcp-web-fetch
Do not conclude an asset is unaffected unless you checked it and the evidence covers both its version and the conditions above. If you could not check something, mark it unknown and say what is missing.
Report a table with one row per asset and these columns: Asset | Version or build | Status (affected, fixed, not applicable, unknown) | Compensating controls | Exposure (internet-facing, internal, none) | Evidence | Next action.
Entry: https://cve.now/CVE-2026-126776
For follow-up questions, use the cve.now MCP server at https://mcp.cve.now/mcp (no authentication), for example execute with name cve.get and arguments {"id": "CVE-2026-126776"}.Timeline
- CVE published
- First seen by cve.now
Affected versions
- siyuan-note siyuan
From 3.7.0 · fixed in 3.8.10
Evidence 7
Vendor advisory · 1
Establishes: Affected and fixed versions.
- Advisory
CVE record · 2
Establishes: The identifier and description.
- Record
- Record
Corrections
None so far.
Something wrong on this page? Report an error. Every fix is listed here.
Questions about CVE-2026-126776
Is CVE-2026-126776 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-2026-126776?
siyuan: from 3.7.0 before 3.8.10.Source: cve.now feed data
How do I fix CVE-2026-126776?
Upgrade to a fixed version: 3.8.10.Source: cve.now feed data