CVE-2026-100646: siyuan · Origin Validation Error
Affects siyuanSource CVE Database V5
Public exploit available · CVSS 8.6 High : upgrade to 3.8.4 as a priority.
Data as of 10 Nov 2026, 23:24 UTC
- EPSS
- 0.2% chance of exploitation in 30 days – higher than 15% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
- CISA SSVC
- Exploitation
- Proof of concept is public or traded
- Automatable
- Attackers cannot reliably automate steps 1–4 of the kill chain
- Technical impact
- Total control over the software or total information disclosure
CISA SSVC assessment, 2026-09-30.
- Patch
- Available – fixed in 3.8.4
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:H/VI:H/VA:N/SC:N/SI:N/SA:NExploitation evidence
t = 0 is the CVE’s publication on cve.org
Disclosed: evidence found.
CVE published 26 Sep 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: evidence found.
CISA SSVC: proof of concept public
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors
Timeline
CVE ID reserved
by VulnCheck
, 11 hours before disclosure
CVE published
on cve.org
, t = 0
CISA SSVC assessment
proof of concept public
, 4 days after disclosure
In Threat Radar
record ingested
, 30 days after disclosure
A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), CISA SSVC, the Metasploit, Exploit-DB and nuclei-templates index as of 10 Nov 2026.
What to do
Upgrade siyuan to 3.8.4.
Affected software
| Product | Affected | Fixed in |
|---|---|---|
| siyuan-notesiyuan | Affected
| Fixed in
|
Gosiyuanpkg:golang/siyuanOther threats | Affected
| Fixed in
|
Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.
AI-suggested
Upgrade SiYuan to version 3.8.4 or later, where this vulnerability is fixed. No other mitigation is indicated by the vendor advisory.
Description
SiYuan versions up to 3.8.3 have an origin validation flaw where the absence of the HTTP Origin header causes authentication checks to fail open. This allows cross-site GET requests from attacker-controlled pages to gain administrator privileges. The vulnerability also enables remote script execution within the SiYuan origin and exfiltration of the kernel API token. The issue is fixed in version 3.8.4.