How severe is CVE-2026-33066?

CVE-2026-33066 has a CVSS 3.x base score of 9.0, rated critical severity. It is exploitable over network with low attack complexity, requires low privileges and user interaction. Impact on confidentiality is high, integrity high, and availability high.

Is CVE-2026-33066 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (44th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2026-33066?

CVE-2026-33066 affects B3log Siyuan. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2026-33066?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its critical severity, prioritise patching exposed systems.

Does CVE-2026-33066 have an EU (EUVD) identifier?

Yes. CVE-2026-33066 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-13628.

When was CVE-2026-33066 published?

CVE-2026-33066 was published on 2026-03-20 and last updated on 2026-06-17.

CVE-2026-33066

CVE-2026-33066 is a critical-severity vulnerability in B3log Siyuan with a CVSS 3.x base score of 9.0. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-79.

Key facts

Severity: Critical (CVSS 3.x base score 9.0)
CVSS v4: 5.3
EPSS exploit prediction: 1% (44th percentile)
Actively exploited: Not listed in CISA KEV
EU (EUVD) id: EUVD-2026-13628
Weakness: CWE-79
Affected product: B3log Siyuan
Published: 2026-03-20
Last modified: 2026-06-17

Description

SiYuan is a personal knowledge management system. In versions 3.6.0 and below, the backend renderREADME function uses lute.New() without calling SetSanitize(true), allowing raw HTML embedded in Markdown to pass through unmodified. The frontend then assigns the rendered HTML to innerHTML without any additional sanitization. A malicious package author can embed arbitrary JavaScript in their README that executes when a user clicks to view the package details. Because SiYuan's Electron configuration enables nodeIntegration: true with contextIsolation: false, this XSS escalates directly to full Remote Code Execution. The issue was patched in version 3.6.1.

Frequently asked questions

What is CVE-2026-33066?: SiYuan is a personal knowledge management system. In versions 3.6.0 and below, the backend renderREADME function uses lute.New() without calling SetSanitize(true), allowing raw HTML embedded in Markdown to pass through unmodified. The frontend then assigns the rendered HTML to innerHTML without any additional sanitization. A malicious package author can embed arbitrary JavaScript in their README that executes when a user clicks to view the package details. Because SiYuan's Electron configuration enables nodeIntegration: true with contextIsolation: false, this XSS escalates directly to full Remote Code Execution. The issue was patched in version 3.6.1.
How severe is CVE-2026-33066?: CVE-2026-33066 has a CVSS 3.x base score of 9.0, rated critical severity. It is exploitable over network with low attack complexity, requires low privileges and user interaction. Impact on confidentiality is high, integrity high, and availability high.
Is CVE-2026-33066 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (44th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2026-33066?: CVE-2026-33066 affects B3log Siyuan. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2026-33066?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its critical severity, prioritise patching exposed systems.
Does CVE-2026-33066 have an EU (EUVD) identifier?: Yes. CVE-2026-33066 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-13628.
When was CVE-2026-33066 published?: CVE-2026-33066 was published on 2026-03-20 and last updated on 2026-06-17.

References

Affected products (1)

cpe:2.3:a:b3log:siyuan:*:*:*:*:*:*:*:*

More vulnerabilities in B3log Siyuan

CVE-2026-32938 — Critical (CVSS 9.9): SiYuan is a personal knowledge management system. In versions 3.6.0 and below, the /api/lute/html2BlockDOM on the…
CVE-2026-33670 — Critical (CVSS 9.8): SiYuan is a personal knowledge management system. Prior to version 3.6.2, the /api/file/readDir interface was used to…
CVE-2026-33669 — Critical (CVSS 9.8): SiYuan is a personal knowledge management system. Prior to version 3.6.2, document IDs were retrieved via the…
CVE-2026-32767 — Critical (CVSS 9.8): SiYuan is a personal knowledge management system. Versions 3.6.0 and below contain an authorization bypass…
CVE-2024-55660 — Critical (CVSS 9.8): SiYuan is a personal knowledge management system. Prior to version 3.1.16, SiYuan's `/api/template/renderSprig`…
CVE-2024-53507 — Critical (CVSS 9.8): A SQL injection vulnerability was discovered in Siyuan 3.1.11 in /getHistoryItems.

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