CVE-2026-87811

HIGH CVSS 4.0: 8.4 EPSS 0.37%
Updated Sep 09, 2026
B3Log
Parameter Value
CVSS 8.4 (HIGH)
Affected Versions before 3.8.2
Fixed In 3.8.2
Type CWE-79 (Cross-Site Scripting (XSS))
Vendor B3Log
Public PoC No

SiYuan before v3.8.2 inserts persisted notebook template paths into HTML input value attributes without proper attribute encoding. Attackers can craft malicious template paths that break out of the attribute context and execute JavaScript when a victim opens notebook configuration, enabling same-origin API requests and application state manipulation.

Attack Parameters

Attack Vector
Network
Can be exploited remotely
Attack Complexity
Low
Easy to exploit
Attack Requirements
None
No additional conditions
Privileges Required
Low
Basic privileges needed
User Interaction
Active
User action required

Impact Assessment

Confidentiality
High
Complete data leak
Integrity
High
Complete data modification
Availability
None
No disruption

CVSS Vector v4.0

Vulnerable Products 1

Configuration From (including) Up to (excluding)
B3log Siyuan
cpe:2.3:a:b3log:siyuan:*:*:*:*:*:*:*:*
— 3.8.2