CVE-2026-100634: Auth Bypass (CVSS 4.7)

Description

SiYuan before v3.8.4 does not validate the sender or restrict recipients in the 'siyuan-send-windows' IPC handler of the Electron main process (app/electron/main.js). The handler ignores event.sender and forwards any received payload to every BrowserWindow returned by BrowserWindow.getAllWindows(), including windows belonging to other opened workspaces. A renderer connected to an attacker-controlled remote kernel can therefore send {cmd: "lockscreenByMode"} and have it delivered across the workspace boundary; a sibling workspace window whose lockScreenMode is set to 1 invokes lockScreen(). Repeated messages allow the remote workspace to repeatedly lock unrelated local workspace windows, causing a limited denial of service. No confidentiality, integrity, or code-execution impact was observed.

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CVSS v3.1 Score

4.7

MEDIUM

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:N/I:N/A:L

EPSS — Exploit Prediction

0.0047

Probability of exploitation

0.39%

Percentile rank

EPSS estimates the probability that this vulnerability will be exploited in the wild within the next 30 days. A higher score means more likely to be exploited.

Weakness Type (CWE)

CWE-862 Missing Authorization

References

Other References

https://github.com/siyuan-note/siyuan/commit/8641553a1f07374001902d3ce773285db1292b2d https://github.com/siyuan-note/siyuan/security/advisories/GHSA-wxp7-xpq8-8xpm https://www.vulncheck.com/advisories/siyuan-before-3.8.4-missing-authorization-via-siyuan-send-windows https://github.com/siyuan-note/siyuan/security/advisories/GHSA-wxp7-xpq8-8xpm

Frequently Asked Questions

What is CVE-2026-100634? +

SiYuan before v3.8.4 does not validate the sender or restrict recipients in the 'siyuan-send-windows' IPC handler of the Electron main process (app/electron/main.js). The handler ignores event.sender and forwards any received payload to every BrowserWindow returned by BrowserWindow.getAllWindows(), including windows belonging to other opened workspaces. A renderer connected to an attacker-controlled remote kernel can therefore send {cmd: "lockscreenByMode"} and have it delivered across the workspace boundary; a sibling workspace window whose lockScreenMode is set to 1 invokes lockScreen(). Repeated messages allow the remote workspace to repeatedly lock unrelated local workspace windows, causing a limited denial of service. No confidentiality, integrity, or code-execution impact was observed. It has a CVSS v3.1 base score of 4.7 (MEDIUM).

How severe is CVE-2026-100634? +

CVE-2026-100634 has a CVSS v3.1 score of 4.7 out of 10, rated MEDIUM. This is a medium-severity vulnerability that should be remediated as part of regular maintenance. The EPSS score is 0.0047, placing it in the 0th percentile for exploitation probability.

How do I check if I'm vulnerable to CVE-2026-100634? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

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