High severity · published Aug 28, 2026
CVE-2026-82234
SiYuan before v3.8.1 SSRF via DNS-Rebinding TOCTOU
8.2
CVSS
0.4%
EPSS
No
On KEV
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.
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:L/A:N
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
Required
Confidentiality
High
Integrity
Low
Availability
None
Scope
Changed
Exploitation
Is it being used?
Exploit prediction (EPSS)0.4% · higher than 30% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
SI
siyuan · siyuan-note
before 3.8.1 · source: vendor
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-82234
CVE.org
https://www.cve.org/CVERecord?id=CVE-2026-82234
github.com
https://github.com/siyuan-note/siyuan/security/advisories/GHSA-x8gv-g2g3-65fj
www.vulncheck.com
https://www.vulncheck.com/advisories/siyuan-before-3.8.1-ssrf-via-dns-rebinding-toctou
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