CVE-2026-72797

Executive Summary

CVE-2026-72797 is a missing-authorization vulnerability (CWE-862) in SiYuan versions before v3.7.4. The getEncryptedNotebookStatus endpoint discloses encrypted notebook identifiers, names, and lock states without publish-access filtering, allowing anonymous unauthenticated readers and publish-mode accounts to enumerate sensitive notebook metadata. The vulnerability is remotely exploitable with no privileges or user interaction, carries a CVSS base score of 5.8, and currently has no confirmed patch, no public exploit code, and no CISA KEV listing.

Technical Analysis

SiYuan is an open-source personal knowledge-management and note-taking application (vendor per CNA data: Thomas Eichmann). When deployed in "publish" mode or exposed to a network, the built-in web interface serves content to readers. The affected component is the getEncryptedNotebookStatus API endpoint.

According to the NVD description, this endpoint "returns encrypted notebook identifiers, names, and lock states without publish-access filtering." The root cause is a missing authorization check on the endpoint: the handler fails to verify whether the requesting principal has publish-level access to the notebook metadata it returns. The description explicitly states that "anonymous readers and publish-mode accounts can enumerate all encrypted notebooks and their current unlock status."

The vulnerability class is CWE-862 (Missing Authorization). It is an access-control flaw, not a memory-corruption or injection issue. The attack surface is any network-facing SiYuan web service, including deployments that intentionally expose a shared/published notebook space. The disclosure includes:

• Encrypted notebook identifiers (stable handles that identify individual notebooks).
• Notebook names (potentially sensitive titles such as client names, project codenames, or personal health/therapy notes).
• Lock states (whether each encrypted notebook is currently locked or unlocked in memory).

The fourth disclosed item, "decryption state in memory," indicates that the endpoint leaks runtime state — i.e., whether the user has already unlocked a notebook in an active session. This is particularly valuable to an attacker because it reveals which encrypted notebooks are currently readable in memory and would therefore be the highest-value targets if additional memory-disclosure or session-hijacking vulnerabilities are discovered.

No code-level trace, proof-of-concept, or official vendor advisory is available in the provided data. The exact URI path, HTTP method, and request/response schema of getEncryptedNotebookStatus are not disclosed by the NVD description, so detection content must key on the endpoint name as it appears in URLs, HTTP request bodies, or application logs.

The CVSS vector (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:N/A:N) confirms the remote, unauthenticated, low-complexity nature of the flaw. Confidentiality impact is rated Low (metadata only, not notebook contents), there is no integrity or availability impact, and the scope is Changed (S:C) because the authorization boundary of the affected component is violated — data belonging to a protected resource class (encrypted notebooks) is exposed through an unprotected API.

Exploitation Scenarios

No public PoC or exploit code is available for CVE-2026-72797 as of this report. The attack chain below is inferred strictly from the vulnerability class (CWE-862, missing authorization on a public-facing API endpoint) and the NVD description. Specific URI paths, HTTP verbs, and JSON schemas are not confirmed.

1. Reconnaissance / target identification: An attacker identifies internet-exposed SiYuan instances. Shodan or Google dorking on "SiYuan" (page title or HTML body) is sufficient to locate candidate hosts. The attacker fingerprints the application and, if version information is accessible, confirms it is older than v3.7.4. Any instance running in publish mode — i.e., a hosted notebook space intended to be shared with readers — is a valid target.

2. Triggering the flaw: The attacker sends an unauthenticated HTTP request to the getEncryptedNotebookStatus endpoint. Because the endpoint lacks publish-access filtering and the application does not require authentication for anonymous readers, no session cookie, API token, or previous interaction is needed. The request is trivial: a single GET (or application-level API call) that reaches the exposed handler.

3. Payload / execution method: There is no injection payload. The "payload" is simply the valid API call itself, made entirely without credentials. This is the defining characteristic of a CWE-862 missing-authorization flaw: the vulnerable endpoint trusts that the caller has permission to view encrypted notebook metadata and never verifies that assumption.

4. Post-exploitation impact: The response discloses the full list of encrypted notebooks: their identifiers, their names, and their current lock/unlock status. The attacker now possesses:

   • A targeted list of notebook names that may reveal confidential business or personal information (client names, project titles, HR matters, health notes).
   • Stable notebook identifiers that can be used in subsequent API calls if other endpoint-level authorization gaps exist.
   • Knowledge of which notebooks are currently unlocked in memory, which informs timing-based or memory-oriented attacks and identifies high-value decrypted data that may be retrievable through other means.

Repeated polling of the endpoint over time can additionally reveal behavioral patterns: when a user unlocks specific notebooks, how many notebooks exist, when new notebooks are created, and when the environment is actively in use.

Impact Assessment

The business impact is primarily confidentiality-related. SiYuan is marketed as a private, local-first note-taking and knowledge-base tool; users store highly sensitive material in it, frequently including client data, proprietary research, journal entries, and corporate secrets. Notebook names alone can reveal organizational structure, ongoing projects, legal matters, or personal medical information, even when the notebook bodies remain encrypted.

The CVSS base score is 5.8 (Medium). Subscore analysis from the vector:

• AV:N / AC:L / PR:N / UI:N — the vulnerability is exploitable remotely over the network by any unauthenticated actor with no special conditions or user interaction.
• S:C (Scope Changed) — the vulnerable authorization check applies to one component (the publish/API layer) while the disclosed data belongs to another protected domain (encrypted notebook storage), crossing a trust boundary.
• C:L — confidentiality loss is limited to metadata and lock state; encrypted notebook contents are not directly exposed by this CVE.
• I:N / A:N — no integrity or availability impact.

Blast radius: any SiYuan instance before v3.7.4 that is reachable by network clients — most notably instances configured for publish mode, which by design accept anonymous readers. The EPSS score (0.00237, ~14.9th percentile of exploited CVEs) indicates that exploitation in the wild is currently unlikely; the CVE is not listed in CISA KEV, and there is no evidence of threat actor campaigns or in-the-wild exploitation as of this report. However, because the endpoint is trivially discoverable and requires no authentication, the practical exploitation barrier is near zero for anyone who runs a routine web inventory scan.

Detection Guidance

The following detection content keys on the verbatim endpoint name getEncryptedNotebookStatus as observed in HTTP traffic and web server logs. Tuning may be required based on the exact web server log format in use, since the NVD description does not disclose the full URI path or HTTP method.

Sigma Rule

title: SiYuan getEncryptedNotebookStatus Unauthenticated Access
id: 8a3c2b1e-4d5f-4a6b-9c1e-7f8a9b0c1d2e
status: experimental
description: >
  Detects HTTP requests referencing the SiYuan getEncryptedNotebookStatus endpoint.
  This endpoint is affected by CVE-2026-72797 and discloses encrypted notebook
  identifiers, names, and lock states without publish-access filtering.
references:
  - https://nvd.nist.gov/vuln/detail/CVE-2026-72797
author: Valtersit Threat Intelligence
date: 2026/01/01
logsource:
  category: webserver
  definition: Web server access logs (Apache, Nginx, IIS) or reverse proxy logs
detection:
  selection_uri:
    c-uri|contains: getEncryptedNotebookStatus
  selection_stem:
    cs-uri-stem|contains: getEncryptedNotebookStatus
  selection_request:
    request|contains: getEncryptedNotebookStatus
  condition: selection_uri or selection_stem or selection_request
falsepositives:
  - Legitimate authenticated requests made by the SiYuan web client itself
level: high
tags:
  - attack.t1190
  - attack.t1213
  - cve.2026-72797
  - cwe.862

YARA Rule

rule CVE_2026_72797_Siyuan_Notebook_Status_Disclosure
{
    meta:
        author      = "Valtersit Threat Intelligence"
        description = "Detects log files, PCAPs, or HTTP transcripts referencing the SiYuan getEncryptedNotebookStatus endpoint associated with CVE-2026-72797 unauthorized encrypted-notebook metadata disclosure."
        cve         = "CVE-2026-72797"
        cwe         = "CWE-862"
        reference   = "https://nvd.nist.gov/vuln/detail/CVE-2026-72797"

    strings:
        $s1 = "getEncryptedNotebookStatus" ascii wide nocase
        $s2 = "notebook" ascii wide nocase
        $s3 = "SiYuan" ascii wide nocase

    condition:
        $s1 and filesize < 100MB
}

Suricata IDS Rule

# Rule 1: Match endpoint name in the HTTP URI
alert http any any -> $HOME_NET any (msg:"CVE-2026-72797 SiYuan getEncryptedNotebookStatus Unauthenticated Enumeration Attempt (URI)"; flow:established,to_server; content:"getEncryptedNotebookStatus"; fast_pattern; nocase; http.uri; reference:cve,2026-72797; reference:url,https://nvd.nist.gov/vuln/detail/CVE-2026-72797; classtype:attempted-recon; sid:20267279701; rev:1;)

# Rule 2: Match endpoint name in the HTTP request body (API-style POST/JSON calls)
alert http any any -> $HOME_NET any (msg:"CVE-2026-72797 SiYuan getEncryptedNotebookStatus Unauthenticated Enumeration Attempt (BODY)"; flow:established,to_server; content:"getEncryptedNotebookStatus"; fast_pattern; nocase; http.request_body; reference:cve,2026-72797; reference:url,https://nvd.nist.gov/vuln/detail/CVE-2026-72797; classtype:attempted-recon; sid:20267279702; rev:1;)

Elastic Detection

any where
  url.full like "*getEncryptedNotebookStatus*" or
  url.path like "*getEncryptedNotebookStatus*" or
  http.request.body.content like "*getEncryptedNotebookStatus*"

Splunk SPL Query

index=web* sourcetype=access_combined OR sourcetype=iis OR sourcetype=nginx*
  ("getEncryptedNotebookStatus")
| eval src=coalesce(src_ip, clientip, c-ip)
| stats earliest(_time) as first_seen latest(_time) as last_seen
        values(uri) as uris count as request_count by src, status, user
| sort - first_seen
| table first_seen, last_seen, src, request_count, uris, status, user

Wazuh OSSEC Rule

<group name="siyuan,">
  <rule id="100084" level="10">
    <decoded_as>web-accesslog</decoded_as>
    <match>getEncryptedNotebookStatus</match>
    <description>CVE-2026-72797 - Unauthenticated access to SiYuan getEncryptedNotebookStatus endpoint (encrypted notebook metadata disclosure)</description>
    <group>cve,siyuan,</group>
    <mitre>
      <id>T1190</id>
    </mitre>
  </rule>
</group>

Mitigation & Patch Guidance

Patch confidence is 0/4: no patch evidence exists from any tracked source, no vendor advisory has been published, and no workarounds have been announced by the vendor. The NVD description's phrasing "versions before v3.7.4" implies that release v3.7.4 is the patched version; however, this is not corroborated by a verified vendor bulletin, and analysts should confirm the fix in the official release notes before treating the CVE as remediated.

Immediate mitigations (until a verified fix is it installed):

1. Restrict network exposure: place any SiYuan instance behind a VPN or authenticated reverse proxy; do not expose publish mode to the internet unless strictly required.
2. If publish mode is not needed for the deployment, disable it entirely.
3. Deploy a WAF or reverse-proxy rule that blocks requests containing the string getEncryptedNotebookStatus originating from unauthenticated/anonymous sources.
4. Use the detection content above to monitor for attempted enumeration and review historical access logs for prior exposure of the endpoint.

Patch / upgrade steps:

1. Confirm the latest SiYuan release; if v3.7.4 or later is available from the vendor, upgrade all affected instances.
2. After upgrading, re-test the getEncryptedNotebookStatus endpoint from an anonymous session to verify it now enforces publish-access filtering.
3. Track the CVE for updates; if the vendor releases a dedicated advisory, follow its migration and compatibility notes.

Long-term hardening:

1. Treat all SiYuan API endpoints as authorization-sensitive; conduct a review of every published endpoint to ensure access-control checks are consistently applied server-side, not just in the UI.
2. Adopt least-privilege deployment: separate publish-facing components from the local note database.
3. Ensure encrypted notebook titles are treated as confidential data in the data model; consider obfuscating or hashing notebook names in server responses.
4. Establish a vulnerability management process for open-source self-hosted applications, including automated version monitoring and regular security testing of exposed API surface.

References

1. NVD Entry: https://nvd.nist.gov/vuln/detail/CVE-2026-72797
2. CVE.org Record: https://www.cve.org/CVERecord?id=CVE-2026-72797
3. FIRST CVSS v3.1 Calculator (vector reference): https://www.first.org/cvss/calculator/3.1#CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:N/A:N
4. SiYuan Official Repository (release notes / version verification): https://github.com/siyuan-note/siyuan

No CISA KEV listing applies to CVE-2026-72797. No known threat actor campaigns, exploit-in-the-wild evidence, public PoC, or Nuclei template activity has been identified as of this report; EPSS (0.00237) indicates a low current likelihood of exploitation, but the unauthenticated nature of the flaw warrants proactive monitoring and patching.