How severe is CVE-2026-34449?

CVE-2026-34449 has a CVSS 3.x base score of 9.6, rated critical severity. It is exploitable over network with low attack complexity, requires no privileges and user interaction. Impact on confidentiality is high, integrity high, and availability high.

Is CVE-2026-34449 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (39th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2026-34449?

CVE-2026-34449 affects B3log Siyuan. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2026-34449?

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-2026-34449 have an EU (EUVD) identifier?

Yes. CVE-2026-34449 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-17676.

When was CVE-2026-34449 published?

CVE-2026-34449 was published on 2026-03-31 and last updated on 2026-06-17.

CVE-2026-34449

CVE-2026-34449 is a critical-severity vulnerability in B3log Siyuan with a CVSS 3.x base score of 9.6. 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-942.

Key facts

Severity: Critical (CVSS 3.x base score 9.6)
EPSS exploit prediction: 0% (39th percentile)
Actively exploited: Not listed in CISA KEV
EU (EUVD) id: EUVD-2026-17676
Weakness: CWE-942
Affected product: B3log Siyuan
Published: 2026-03-31
Last modified: 2026-06-17

Description

SiYuan is a personal knowledge management system. Prior to version 3.6.2, a malicious website can achieve Remote Code Execution (RCE) on any desktop running SiYuan by exploiting the permissive CORS policy (Access-Control-Allow-Origin: * + Access-Control-Allow-Private-Network: true) to inject a JavaScript snippet via the API. The injected snippet executes in Electron's Node.js context with full OS access the next time the user opens SiYuan's UI. No user interaction is required beyond visiting the malicious website while SiYuan is running. This issue has been patched in version 3.6.2.

Frequently asked questions

What is CVE-2026-34449?: SiYuan is a personal knowledge management system. Prior to version 3.6.2, a malicious website can achieve Remote Code Execution (RCE) on any desktop running SiYuan by exploiting the permissive CORS policy (Access-Control-Allow-Origin: * + Access-Control-Allow-Private-Network: true) to inject a JavaScript snippet via the API. The injected snippet executes in Electron's Node.js context with full OS access the next time the user opens SiYuan's UI. No user interaction is required beyond visiting the malicious website while SiYuan is running. This issue has been patched in version 3.6.2.
How severe is CVE-2026-34449?: CVE-2026-34449 has a CVSS 3.x base score of 9.6, rated critical severity. It is exploitable over network with low attack complexity, requires no privileges and user interaction. Impact on confidentiality is high, integrity high, and availability high.
Is CVE-2026-34449 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (39th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2026-34449?: CVE-2026-34449 affects B3log Siyuan. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2026-34449?: 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-2026-34449 have an EU (EUVD) identifier?: Yes. CVE-2026-34449 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-17676.
When was CVE-2026-34449 published?: CVE-2026-34449 was published on 2026-03-31 and last updated on 2026-06-17.

References

Affected products (1)

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

More vulnerabilities in B3log Siyuan

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Other CWE-942 vulnerabilities

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CVE-2026-9739 — Critical (CVSS 9.4): Vulnerable to DNS rebinding attacks when using SSE (http://b/499408790). During the beta phase, we implemented…
CVE-2026-8948 — Critical (CVSS 9.1): Same-origin policy bypass in the DOM: Networking component. This vulnerability was fixed in Firefox 151 and Thunderbird…
CVE-2023-38125 — High (CVSS 8.8): Softing edgeAggregator Permissive Cross-domain Policy with Untrusted Domains Remote Code Execution Vulnerability. This…

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