SiYuan CVE-2026-74801

Exploitation requires four specific conditions: (1) the attacker must have local access as a low-privileged user (PR:L per CVSS vector); (2) the attacker must be able to create or control a SiYuan workspace directory whose filesystem path contains OS command metacharacters; (3) the victim user must explicitly trigger the Microsoft Defender exclusion workflow within the SiYuan application - this is not a passive or automatic action; and (4) the victim must approve the Windows UAC elevation prompt that SiYuan displays before invoking elevator.exe (UI:P per CVSS vector). This vulnerability is Windows-only - the elevator.exe helper and Defender exclusion flow do not exist on macOS or Linux. The UAC approval step is the key limiting factor: exploitation cannot succeed silently without user consent, which reduces risk in environments with standard UAC policies but does not eliminate it in cases where an attacker can social-engineer or wait for the target to organically use the Defender exclusion feature.

The CVSS 4.0 vector (AV:L/AC:L/AT:N/PR:L/UI:P/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H) scores 8.6, with subsequent-system impact metrics all at High - indicating potential full system compromise beyond the SiYuan process itself. AV:L and PR:L confirm this is a local, low-privilege attack, not remotely exploitable. UI:P reflects the passive user interaction requirement: the victim must trigger the Defender exclusion flow and approve a UAC prompt. This two-step human interaction is a meaningful friction point that reduces opportunistic exploitation risk compared to zero-interaction vulnerabilities. No EPSS score was provided in the intelligence feed, so statistical exploitation probability is unknown. No CISA KEV listing is present, and no POC code is referenced in the available data, so exploitation remains theoretical at time of analysis. The attack complexity is low once an attacker has pre-positioned a malicious workspace, suggesting this is exploitable without specialized knowledge. Real-world priority is moderate: high impact if exploited, but requires local access, a specific user action, and UAC consent - making mass exploitation unlikely, while targeted insider or supply-chain scenarios remain plausible.

An attacker with a local low-privileged account creates a SiYuan workspace at a path such as C:\legit\dir & calc.exe & - embedding an arbitrary command in the directory name using shell metacharacters. When the targeted user later navigates the SiYuan interface to add a Microsoft Defender exclusion for that workspace and clicks through the resulting UAC prompt, SiYuan passes the unsanitized path string to elevator.exe, which causes the injected command (in this example, calc.exe, or a more malicious payload) to execute with administrator privileges. No public POC has been identified at time of analysis.