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CVE-2026-25539 β€” AI Deep Analysis Summary

CVSS 9.1 Β· Critical

Q1What is this vulnerability? (Essence + Consequences)

🚨 **Essence**: A Path Traversal flaw in SiYuan's `/api/file/copyFile` endpoint. πŸ“‰ **Consequences**: Attackers can write files to arbitrary locations, potentially leading to **Remote Code Execution (RCE)**.…

Q2Root Cause? (CWE/Flaw)

πŸ›‘οΈ **CWE-22**: Improper Limitation of a Pathname to a Restricted Directory. πŸ’₯ **Flaw**: The `dest` parameter in the copy API is **not validated**. No sanitization of directory traversal sequences (e.g., `../`).

Q3Who is affected? (Versions/Components)

πŸ“¦ **Product**: SiYuan (Privacy-first personal knowledge management system). πŸ‘₯ **Affected**: Versions **prior to 3.5.5**. If you are running <3.5.5, you are vulnerable!

Q4What can hackers do? (Privileges/Data)

πŸ’€ **Hackers' Power**: Can overwrite system files or config files. 🎯 **Goal**: Achieve **Remote Code Execution**. πŸ’Ύ **Data**: Full read/write access to the file system, bypassing intended sandboxing.

Q5Is exploitation threshold high? (Auth/Config)

πŸ” **Threshold**: **Medium**. Requires **High Privileges (PR:H)** according to CVSS. You likely need to be a logged-in user with sufficient permissions to trigger the API call. Not fully anonymous.

Q6Is there a public Exp? (PoC/Wild Exploitation)

πŸ•΅οΈ **Exploit Status**: **No public PoC** listed in the data. 🌐 **Wild Exploitation**: Unconfirmed. However, the logic flaw is clear, making custom exploits likely possible for skilled attackers.

Q7How to self-check? (Features/Scanning)

πŸ” **Self-Check**: Scan for SiYuan instances. πŸ§ͺ **Test**: Try accessing `/api/file/copyFile` with a `dest` parameter containing `../`. If the server accepts it without error or blocks it improperly, you are at risk.…

Q8Is it fixed officially? (Patch/Mitigation)

βœ… **Fixed**: **Yes**. Patch released in **SiYuan 3.5.5**. πŸ“ **Commit**: `d7f790755edf8c78d2b4176171e5a0cdcd720feb`. πŸ›‘οΈ **Action**: Update immediately to the latest version.

Q9What if no patch? (Workaround)

🚧 **No Patch?**: If you cannot update, **disable external access** to the API. 🚫 **Restrict**: Limit network exposure. Use strong authentication. Monitor logs for suspicious file copy attempts. Treat as critical risk.

Q10Is it urgent? (Priority Suggestion)

πŸ”₯ **Urgency**: **HIGH**. 🚨 **Priority**: Patch immediately. CVSS Score is **High** (likely 8.0+ based on vector). RCE potential makes this a top-priority fix for any SiYuan admin.