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CVE Record

CVE-2026-23851: SiYuan Vulnerable to Arbitrary File Read via File Copy Functionality

SiYuan is a personal knowledge management system. Versions prior to 3.5.4 contain a logic vulnerability in the /api/file/globalCopyFiles endpoint. The function allows authenticated users to copy files from any location on the server's filesystem into the application's workspace without proper path validation. The vulnerability exists in the api/file.go source code. The function globalCopyFiles accepts a list of source paths (srcs) from the JSON request body. While the code checks if the source file exists using filelock.IsExist(src), it fails to validate whether the source path resides within the authorized workspace directory. Version 3.5.4 patches the issue.

HighCVSS 8.3Not KEV-listedUpdated
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Glexia's TakeAutomated analysishigh

Security readout for executives and security teams

Plain-English summary

SiYuan versions before 3.5.4 let a logged-in user copy server files into the application workspace. This can expose sensitive files from the host system. The issue is serious for shared or remotely accessible SiYuan deployments, but the sources do not show active exploitation.

Executive priority

Prioritize patching if SiYuan is used by multiple users or exposed beyond a trusted local environment. The main business risk is unauthorized disclosure of sensitive server-side files.

Technical view

CVE-2026-23851 is a CWE-22 path validation flaw in SiYuan's /api/file/globalCopyFiles endpoint. The handler accepts source paths and checks existence, but does not verify that sources are within the authorized workspace. An authenticated user could read arbitrary server files by copying them into the workspace. Fixed in 3.5.4.

Likely exposure

Deployments running siyuan-note/siyuan before 3.5.4 are affected. Exposure is higher where untrusted users have accounts or the service is reachable over a network.

Exploitation context

The CVSS v4 score is 8.3. Attack requires authentication, low complexity, no user interaction, and can cause high confidentiality impact. CISA KEV is false in the provided data, and no cited source reports active exploitation.

Researcher notes

Focus review on api/file.go and the globalCopyFiles path authorization logic. The public record names two fixing commits and the GHSA. Evidence supports arbitrary file read after authentication; it does not support unauthenticated exploitation or code execution.

Mitigation direction

  • Upgrade SiYuan to version 3.5.4 or later.
  • Review the GitHub security advisory for vendor guidance.
  • Restrict SiYuan access to trusted users until upgraded.
  • Reduce network exposure for shared or internet-reachable instances.

Validation and detection

  • Inventory SiYuan deployments and confirm installed versions.
  • Flag any instance running below 3.5.4.
  • Confirm authentication is required for SiYuan API access.
  • Review user access, especially on shared deployments.
  • Check vendor advisory and linked commits for patch confirmation.
Prepared
Confidence
high
Sources
6

Public sources used

Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.

Potential ATT&CK relevance

Conservative CVE-to-ATT&CK context

These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.

ATT&CK lookup starting points

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cwe · medium confidence lookup

CWE-22: File access and web shell behavior lookup

File traversal and upload weaknesses can lead teams to review file, web shell, execution, and collection telemetry. Open the exact CWE lookup page first, then review the ATT&CK searches from that MITRE weakness context. This is a Glexia lookup hint, not an official ATT&CK mapping.

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description · low confidence lookup

File access behavior lookup

The CVE wording references file access or upload behavior, so file telemetry and web shell review may help. This is a Glexia inferred lookup path, not an official MITRE, ATT&CK, or CVE Program mapping.

Open ATT&CK lookup
cve · low confidence lookup

CVE-2026-23851 mapping review

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Vulnerability profileCVE Program record
Severity
High
CVSS
8.3 (4.0)
Known Exploited
No
Published

Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:H/VI:N/VA:N/SC:H/SI:N/SA:N

Official CVE source material

CNA and ADP enrichment extracted from CVE v5

These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.

1CVSS vectors
0Timeline events
0ADP providers
5Source links

CVSS vector scores

1 official score

We collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.

ScoreVersionSeverityVectorExploitImpactSource
8.3CVSS 4.0HighCVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:H/VI:N/VA:N/SC:H/SI:N/SA:N——Primary CVE score

Vulnerability scoring details

Base CVSS 4.0 score

8.3High
CVSS 4.0 vector shape for CVE-2026-23851Attack VectorAttack ComplexityAttack RequirementsPrivileges RequiredUser InteractionVS ConfidentialityVS IntegrityVS AvailabilitySS ConfidentialitySS IntegritySS Availability

Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:H/VI:N/VA:N/SC:H/SI:N/SA:N

Attack Vector
NetworkAdjacentLocalPhysical
Attack Complexity
LowHigh
Attack Requirements
NonePresent
Privileges Required
NoneLowHigh
User Interaction
NonePassiveActive
VS Confidentiality
HighLowNone
VS Integrity
HighLowNone
VS Availability
HighLowNone
SS Confidentiality
HighLowNone
SS Integrity
HighLowNone
SS Availability
HighLowNone

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
siyuan-notesiyuan< 3.5.4Listed
Weakness

CWE details

CWE-22

CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.