cve.bz

CVE-2026-126265 SiYuan 2.1.0 before 3.8.9 CAPTCHA Bypass via Stale Login Cookie

9.1 criticalEPSS 0.4%

Critical (9.1) in siyuan-note siyuan. EPSS 0.4% estimated probability of exploitation activity in the next 30 days.

On this page
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.

Severity

CVSS 4.0

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

CVSS 3.1

7.4 high
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N
EPSS
0.4% estimated probability of exploitation activity in the next 30 days; 30th percentile. Scored 2026-11-13. A forecast for this CVE across the internet, not for your own systems.
CWE
CWE-307 Improper Restriction of Excessive Authentication Attempts
OWASP Top 10
A07:2025 Authentication Failures
Published
Modified
Assigned by
VulnCheck (CNA)
NVD analysis
Deferred: the NVD does not plan to analyze it
Record from
the NVD, synced

Ask an AI about this CVE

ChatGPTClaudeGoogle AI Mode

Show the promptExplain CVE-2026-126265 for an engineer deciding whether to act. Use https://cve.bz/api/public/cves/CVE-2026-126265?via=ask-ai-copy and https://cve.bz/cve/CVE-2026-126265?via=ask-ai-copy as the source of truth: what is affected and which versions fix it, whether it is in CISA KEV, public exploits, and its EPSS (an internet-wide 30-day estimate of exploitation activity, not a forecast for my systems). If they give no fixed versions, use the CVE record https://cveawg.mitre.org/api/cve/CVE-2026-126265 or the vendor advisory, not third-party mirrors. Tell me how to check whether I am affected and how to verify a fix. Cite the sources and say where they are uncertain.

Opens a third-party assistant; its answer is its own, not cve.bz's. The prompt holds only this CVE's id and public links.

Badge for a README or a site

CVE-2026-126265

An image that stays current: it is drawn from the data each time it is fetched (a host that proxies images, as GitHub does, may show its copy for a while). Markdown:

[![CVE-2026-126265](https://cve.bz/cve/badge/CVE-2026-126265.svg)](https://cve.bz/cve/CVE-2026-126265)

HTML:

<a href="https://cve.bz/cve/CVE-2026-126265"><img src="https://cve.bz/cve/badge/CVE-2026-126265.svg" alt="CVE-2026-126265"></a>

Affected

Versions

From the CNA's record in the CVE List.

ProductAffected
siyuan-note siyuanfrom 2.1.0 before 3.8.9

Attack patterns (CAPEC)

  • CAPEC-16 Dictionary-based Password Attack Likelihood: Medium · Severity: High
  • CAPEC-49 Password Brute Forcing Likelihood: Medium · Severity: High
  • CAPEC-560 Use of Known Domain Credentials Likelihood: High · Severity: High
  • CAPEC-565 Password Spraying Likelihood: High · Severity: High
  • CAPEC-600 Credential Stuffing Likelihood: High · Severity: High
  • CAPEC-652 Use of Known Kerberos Credentials Likelihood: Medium · Severity: High
  • CAPEC-653 Use of Known Operating System Credentials Likelihood: High · Severity: High

The attack patterns MITRE's CAPEC relates to this record's weaknesses, as MITRE names them. Credits.

History

  1. The NVD deferred its analysis

Changes since this site first stored the record. The same for every record: /api/public/changes.

References

Check your stackJSON