CVE-2026-34449
B3Log Siyuan ≤ 3.6.2
Raw vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:HSummary
CVE-2026-34449 is a critical-severity Permissive Cross-domain Security Policy with Untrusted Domains (CWE-942) vulnerability in B3Log Siyuan. Its CVSS base score is 9.6 (Critical).
Operationally, exploitation aligns with the MITRE ATT&CK technique Drive-by Compromise (T1189); ranked at the 40th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog; a public proof-of-concept is referenced.
The strongest mitigations our analysis identified map to AC-4 (Information Flow Enforcement) and SC-7 (Boundary Protection) — see the control section below for these in your framework.
Deeper analysis AI-assisted summary
Synthesised by an AI model from the NVD description and linked references — a reading aid, not an authoritative source.
CVE-2026-34449 is a high-severity remote code execution (RCE) vulnerability affecting SiYuan, an open-source personal knowledge management system built on Electron. In versions prior to 3.6.2, the application exposes a permissive CORS policy (Access-Control-Allow-Origin: * and Access-Control-Allow-Private-Network: true) on its API endpoints. This allows a malicious website to inject arbitrary JavaScript snippets, which persist and execute in Electron's Node.js runtime context—the next time the user interacts with SiYuan's UI—granting attackers full operating system access on the victim's desktop. The vulnerability is tracked under CWE-942 (Permissive Cross-domain Policy with Untrusted Domains) and carries a CVSS v3.1 base score of 9.6 (AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:H).
Any remote attacker controlling a malicious website can exploit this vulnerability without authentication or privileges. The attack requires the victim to visit the attacker's site while SiYuan is running in the background; no additional user interaction is needed beyond that. Upon subsequent opening of SiYuan's UI, the injected JavaScript executes seamlessly in the Node.js context, enabling full RCE. This could allow attackers to steal data, install malware, or perform other arbitrary actions with the privileges of the SiYuan process, typically those of the logged-in user.
The issue has been fully patched in SiYuan version 3.6.2, as detailed in the project's GitHub release notes and security advisory (GHSA-68p4-j234-43mv). Security practitioners should advise users to update immediately to mitigate risk, with further technical details available in the associated GitHub issue (#17246).
OWASP Top 10 for Web (2025)
EU & UK References
- 🇪🇺 ENISA EUVD: EUVD-2026-17676
Vulnerability Data
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…
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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.
- CWE(s)
Related Threats
MITRE ATT&CK Enterprise Techniques
CVEs Like This One
Affected Assets
Mitigating Controls
Control response
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V3.4.3V3.4.6V3.5.2
Mitigating Controls (NIST 800-53 r5) AI
Information flow enforcement requires approved authorizations and would reject policies permitting untrusted domains.
Boundary protection at external interfaces stops unauthorized cross-domain communication allowed by permissive policies.
Mitigating Controls (NIST CSF 2.0) AI
Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→CSF cross-walk (authority under review) — links open the control.
Hardened configuration baselines and reviews directly prevent permissive CSP or cross-domain policies.
Secure SDLC activities include review and testing of web security policies to avoid untrusted domains.
Vulnerability identification processes can surface permissive policy misconfigurations.
Mitigating Controls (ISO/IEC 27001:2022 Annex A) AI
Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→ISO cross-walk (authority under review) — links open the control.
Security testing can detect overly permissive cross-domain policies but does not prevent their initial introduction.
Network security policies can restrict cross-domain communication but do not specifically mandate strict CSP or cross-domain policy configuration.
Security of network services includes defining allowed endpoints, which can limit untrusted domains but does not directly address web-client policy files.
Web filtering can block untrusted domains at the network level, partially mitigating permissive cross-domain policies.
Application security requirements should specify secure CSP and cross-domain policy settings, directly addressing the weakness.
Secure architecture principles include defining trust boundaries, which can reduce permissive cross-domain allowances.