by Kastro
Paper/Archive/CVE-2026-126265

CVE-2026-126265

siyuan-note siyuan — SiYuan 2.1.0 before 3.8.9 CAPTCHA Bypass via Stale Login Cookie

CVSS 9.1
critical.is priorityof 100
27
CVSS 9.1 (CNA)9.1 / 10 × 3027.3Not in CISA KEV+300.0No EPSS score.000 × 200.0No public exploit+100.0SSVC exploitation: unknown+100.0
Description · from the CVE record

SiYuan 2.1.0 before 3.8.9 contains a flaw where the loginAuth CAPTCHA challenge lives in a signed client-side cookie, allowing reuse of a solved challenge. Attackers can replay the original signed siyuan cookie with distinct wrong access codes to brute-force the code and gain an administrator session.

Affected

ProductAffectedFixed inSource
siyuan2.1.0 – < 3.8.93.8.9CNA

Scores by source

VulnCheck (CNA)9.1CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N
VulnCheck (CNA)7.4CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N

References

advisorygithub.com/siyuan-note/siyuan/security/advisories/GHSA-23g4-vqq8-5764writeupvulncheck.com/advisories/siyuan-2.1.0-before-3.8.9-captcha-bypass-via-stale-login-cookie