CVE-2026-100635

high

Description

SiYuan before v3.8.4 contains an authentication bypass vulnerability in the publish service where session cookies are issued without Secure or SameSite attributes over plaintext HTTP connections. An on-path attacker can observe a valid publish-visitor-session-id cookie from a Basic Auth exchange and replay it to access authenticated publish endpoints without knowing the account password.

References

https://www.vulncheck.com/advisories/siyuan-before-3.8.4-authentication-bypass-via-plaintext-session-cookie

https://github.com/siyuan-note/siyuan/security/advisories/GHSA-7j37-4gq6-wm7m

https://github.com/siyuan-note/siyuan/commit/ff4d215f78a8d6e6db6052be18b5f9f4db9c7d68

https://github.com/siyuan-note/siyuan/commit/79d47867b106467c951475a9193455b48d1f3682

https://euvd.enisa.europa.eu/vulnerability/EUVD-2026-87729

Details

Source: Mitre, NVD

Published: 2026-09-26

Updated: 2026-10-08

Risk Information

CVSS v2

Base Score: 5.4

Vector: CVSS2#AV:N/AC:H/Au:N/C:C/I:N/A:N

Severity: Medium

CVSS v3

Base Score: 5.9

Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N

Severity: Medium

CVSS v4

Base Score: 8.2

Vector: CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N

Severity: High

EPSS

EPSS: 0.00327