CVE-2026-30926
Published: 10 March 2026
Summary
CVE-2026-30926 is a high-severity Improper Access Control (CWE-284) vulnerability in B3Log Siyuan. Its CVSS base score is 7.1 (High).
Operationally, exploitation aligns with the MITRE ATT&CK technique Exploitation for Privilege Escalation (T1068); ranked at the 2.8th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog; a public proof-of-concept is referenced.
Threat & Defense at a Glance
Threat & Defense Details
Likely Mitigating ControlsAI
Per-CVE control mapping for this CVE has not run yet; the list below is derived from the weakness types (CWEs) cited in the NVD entry.
The access control policy and procedures directly mandate and enforce proper access control mechanisms across the organization.
Supervision and review of access control activities directly detects and remediates improper access configurations or usages.
Explicitly identifying and documenting actions permitted without identification or authentication enforces proper access control boundaries by defining justified exceptions.
Associating and retaining security attributes with data directly supports enforcement of access control decisions across storage, processing, and transmission.
Requiring prior authorization for each remote access type prevents improper access control over remote connections.
Requiring authorization of wireless access before allowing connections enforces proper access control for this access method.
Requiring authorization and configuration controls for mobile device connections directly enforces access control and prevents unauthorized devices from reaching organizational systems.
Defining account types, requiring approvals for creation, specifying authorizations, monitoring usage, and reviewing accounts directly prevents improper access control by ensuring only authorized accounts exist and are used.
MITRE ATT&CK Enterprise TechniquesAI
Why these techniques?
The CVE is explicitly a privilege escalation vulnerability due to missing authorization checks (only basic CheckAuth allowing RoleReader), enabling low-priv authenticated users to perform unauthorized modifications via the /api/block/appendHeadingChildren endpoint.
NVD Description
SiYuan is a personal knowledge management system. Prior to 3.5.10, a privilege escalation vulnerability exists in the publish service of SiYuan Note that allows low-privilege publish accounts (RoleReader) to modify notebook content via the /api/block/appendHeadingChildren API endpoint. The endpoint requires…
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only the model.CheckAuth role, which accepts RoleReader sessions, but it does not enforce stricter checks, such as CheckAdminRole or CheckReadonly. This allows remote authenticated publish users with read-only privileges to append new blocks to existing documents, compromising the integrity of stored notes.
Deeper analysisAI
CVE-2026-30926 is a privilege escalation vulnerability in SiYuan, a personal knowledge management system also known as SiYuan Note. Affecting versions prior to 3.5.10, the issue resides in the publish service, specifically the /api/block/appendHeadingChildren API endpoint. This endpoint performs only a basic model.CheckAuth role check, which permits RoleReader sessions, without enforcing stricter authorization such as CheckAdminRole or CheckReadonly. As a result, low-privilege users can append new blocks to existing documents, leading to improper access control (CWE-284, CWE-862). The vulnerability carries a CVSS v3.1 base score of 7.1 (AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:H/A:N).
An attacker with a remote authenticated RoleReader account in the publish service can exploit this vulnerability without user interaction. By sending crafted requests to the vulnerable API endpoint, they can modify notebook content by appending headings or child blocks, thereby compromising the integrity of stored notes despite read-only privileges.
The GitHub Security Advisory (GHSA-f9cq-v43p-v523) details the issue and recommends upgrading to SiYuan version 3.5.10 or later, where the authorization checks have been strengthened to prevent unauthorized modifications.
Details
- CWE(s)