VulnerabilityPublished 4 Feb 2026

CVE-2026-25539: siyuan · Path Traversal

Affects siyuanSource CVE Database V5

Not known to be exploited · CVSS 9.1 Critical : upgrade to 3.5.5 as a priority.

Data as of 26 Oct 2026, 17:16 UTC

CVSS 3.1 base score

9.1Critical

How severe the flaw is on the 0–10 CVSS scale.

EPSS: 1.1% chance of exploitation in 30 days – higher than 65% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch: Available – fixed in 3.5.5

CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:C/C:H/I:H/A:H

Attack Vector: Network
Attack Complexity: Low
Privileges Required: High
User Interaction: None
Scope: Changed
Confidentiality: High
Integrity: High
Availability: High

Bold values are the worst case: easiest to exploit or largest impact.

Attack Vector: Network: The vulnerable component is bound to the network stack and the set of possible attackers extends beyond the other options listed, up to and including the entire Internet. Such a vulnerability is often termed 'remotely exploitable' and can be thought of as an attack being exploitable at the protocol level one or more network hops away (e.g., across one or more routers).
Attack Complexity: Low: Specialized access conditions or extenuating circumstances do not exist. An attacker can expect repeatable success against the vulnerable component.
Privileges Required: High: The attacker is authorized with (i.e., requires) privileges that provide significant (e.g., administrative) control over the vulnerable component that could affect component-wide settings and files.
User Interaction: None: The vulnerable system can be exploited without any interaction from any user.
Scope: Changed: An exploited vulnerability can affect resources beyond the security scope managed by the security authority of the vulnerable component. In this case, the vulnerable component and the impacted component are different and managed by different security authorities.
Confidentiality: High: There is total loss of confidentiality, resulting in all resources within the impacted component being divulged to the attacker. Alternatively, access to only some restricted information is obtained, but the disclosed information presents a direct, serious impact.
Integrity: High: There is a total loss of integrity, or a complete loss of protection. For example, the attacker is able to modify any/all files protected by the impacted component. Alternatively, only some files can be modified, but malicious modification would present a direct, serious consequence to the impacted component.
Availability: High: There is total loss of availability, resulting in the attacker being able to fully deny access to resources in the impacted component; this loss is either sustained (while the attacker continues to deliver the attack) or persistent (the condition persists even after the attack has completed). Alternatively, the attacker has the ability to deny some availability, but the loss of availability presents a direct, serious consequence to the impacted component (e.g., the attacker cannot disrupt existing connections, but can prevent new connections; the attacker can repeatedly exploit a vulnerability that, in each instance of a successful attack, leaks a only small amount of memory, but after repeated exploitation causes a service to become completely unavailable).

Definitions: FIRST CVSS v3.1 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 4 Feb 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponised: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 26 Oct 2026.

Disclosed: The CVE record is public on cve.org. Its publication is t = 0.
Detectable: A public nuclei template can find exposed instances, for defenders and attackers alike.
Weaponised: Public exploit code exists in Metasploit or Exploit-DB, or CISA SSVC or the CVSS exploit maturity reports a public proof of concept.
Exploited in the wild: CISA KEV lists it, CISA SSVC rates exploitation active, or a source reports attacks.
Observed by OffSeq Mirage: OffSeq Mirage honeypot sensors recorded attack traffic for this CVE, or found exposed hosts without attack traffic.

Moments are spaced evenly, not to scale; a dashed line marks a gap of six months or more. Deltas count from t = 0. Sources that give only a date (CISA KEV, Exploit-DB, or a time of exactly 00:00Z) read “same day” rather than hours. Metasploit modules carry the flaw’s disclosure date, not their release date, and nuclei templates carry no date, so both appear above but not on the timeline.

What to do

Upgrade siyuan and siyuan-note/siyuan to 3.5.5.

Affected software

Product	Affected	Fixed in
siyuan-notesiyuan	Affected <3.5.5	Fixed in 3.5.5
GitHubsiyuan-note/siyuan`pkg:github/siyuan-note/siyuan`Other threats	Affected <3.5.5	Fixed in 3.5.5

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

AI-suggested

European organizations should immediately upgrade all SiYuan installations to version 3.5.5 or later to apply the official patch. Until upgrades can be completed, restrict access to the /api/file/copyFile endpoint through network segmentation and firewall rules, limiting it to trusted users only. Implement strict authentication and authorization controls, including multi-factor authentication (MFA), to reduce the risk of credential compromise. Conduct thorough audits of user privileges to ensure only necessary users have access to SiYuan’s file operations. Monitor logs for unusual file write activities or attempts to access sensitive filesystem locations. Employ application-layer firewalls or runtime application self-protection (RASP) solutions to detect and block path traversal attempts. Additionally, review and harden system configurations to minimize the impact of potential file overwrites, such as restricting cron job and SSH authorized_keys file permissions. Regularly back up critical configuration files and maintain an incident response plan tailored to potential RCE scenarios.

Description

CVE-2026-25539 is a critical path traversal vulnerability in the SiYuan personal knowledge management system versions prior to 3.5.5. The flaw exists in the /api/file/copyFile endpoint, where the dest parameter is not properly validated, allowing authenticated users to write files to arbitrary filesystem locations. Exploitation can lead to remote code execution by overwriting sensitive files such as cron jobs, SSH authorized_keys, or shell configuration files. The vulnerability requires authentication but no user interaction and has a CVSS score of 9.1, reflecting its high impact on confidentiality, integrity, and availability. Although no known exploits are reported in the wild, the issue is severe and has been patched in version 3.5.5.

Impact

For European organizations, exploitation of this vulnerability could lead to complete system compromise, data breaches, and disruption of services. Attackers could gain persistent remote code execution capabilities, enabling them to deploy malware, exfiltrate sensitive data, or disrupt operations. This is particularly concerning for organizations that use SiYuan for managing confidential knowledge or intellectual property. The ability to overwrite critical system files could also facilitate lateral movement within networks, increasing the risk of widespread compromise. Given the high severity and the potential for privilege escalation, the impact extends beyond individual systems to organizational security posture and regulatory compliance, especially under GDPR where data protection is paramount. The requirement for authentication limits exposure but does not eliminate risk, as insider threats or compromised credentials could be leveraged. The absence of known exploits in the wild suggests a window for proactive mitigation before widespread attacks occur.

CWE-22Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal') (opens in a new tab)
Base weaknessLikelihood of exploit: HighCWE Top 25 (2025): #6OWASP Top 10 A01:2025: Broken Access Control (opens in a new tab)
The product uses external input to construct a pathname that is intended to identify a file or directory that is located underneath a restricted parent directory, but the product does not properly neutralize special elements within the pathname that can cause the pathname to resolve to a location that is outside of the restricted directory.
Implementation · Input Validation
Assume all input is malicious. Use an "accept known good" input validation strategy, i.e., use a list of acceptable inputs that strictly conform to specifications. Reject any input that does not strictly conform to specifications, or transform it into something that does.
Architecture and Design
For any security checks that are performed on the client side, ensure that these checks are duplicated on the server side, in order to avoid CWE-602. Attackers can bypass the client-side checks by modifying values after the checks have been performed, or by changing the client to remove the client-side checks…
Implementation · Input Validation
Inputs should be decoded and canonicalized to the application's current internal representation before being validated (CWE-180). Make sure that the application does not decode the same input twice (CWE-174).
OWASP Cheat Sheets
Authorization (opens in a new tab)
OWASP ASVS 4.0.3
V12.3.1 (opens in a new tab)
Attack patterns
Path Traversal (opens in a new tab)
Using Slashes and URL Encoding Combined to Bypass Validation Logic (opens in a new tab)
Manipulating Web Input to File System Calls (opens in a new tab)
Using Escaped Slashes in Alternate Encoding (opens in a new tab)
Using Slashes in Alternate Encoding (opens in a new tab)
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).

References

Community reviews

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 12 Feb 2026, 07:30 UTC

WeaknessesCWE-22

Technical details

References

Community reviews

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