CVE-2026-100635: Cleartext Transmission of Sensitive Information in siyuan-note siyuan
SiYuan before v3.8.4 contains an authentication bypass vulnerability in the publish service where session cookies are issued without Secure or SameSite attributes over plaintext HTTP connections. An on-path attacker can observe a valid publish-visitor-session-id cookie from a Basic Auth exchange and replay it to access authenticated publish endpoints without knowing the account password.
AI Analysis
Technical Summary
CVE-2026-100635 describes an authentication bypass in SiYuan note software prior to version 3.8.4. The vulnerability arises from session cookies (publish-visitor-session-id) being transmitted over plaintext HTTP without Secure or SameSite flags. An attacker on the network path can intercept these cookies during a Basic Auth exchange and replay them to gain unauthorized access to authenticated publish endpoints, bypassing password authentication.
Potential Impact
An attacker with network access can capture session cookies transmitted without encryption and reuse them to access authenticated publish endpoints without credentials. This compromises the confidentiality and integrity of the publish service sessions, potentially allowing unauthorized data access or manipulation.
Mitigation Recommendations
Upgrade SiYuan to version 3.8.4 or later where this issue is fixed. The vulnerability is resolved by ensuring session cookies are properly secured and transmitted only over encrypted connections. Until upgraded, avoid using the publish service over unencrypted HTTP connections to reduce risk.
CVE-2026-100635: Cleartext Transmission of Sensitive Information in siyuan-note siyuan
Description
SiYuan before v3.8.4 contains an authentication bypass vulnerability in the publish service where session cookies are issued without Secure or SameSite attributes over plaintext HTTP connections. An on-path attacker can observe a valid publish-visitor-session-id cookie from a Basic Auth exchange and replay it to access authenticated publish endpoints without knowing the account password.
CVSS v4.0
Score 8.2high
Affected software
siyuan-note
siyuan
pkg:github/siyuan-note/siyuanRun on your own infrastructure? Check whether these packages are installed with threat-finder — our free open-source scanner.
AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
CVE-2026-100635 describes an authentication bypass in SiYuan note software prior to version 3.8.4. The vulnerability arises from session cookies (publish-visitor-session-id) being transmitted over plaintext HTTP without Secure or SameSite flags. An attacker on the network path can intercept these cookies during a Basic Auth exchange and replay them to gain unauthorized access to authenticated publish endpoints, bypassing password authentication.
Potential Impact
An attacker with network access can capture session cookies transmitted without encryption and reuse them to access authenticated publish endpoints without credentials. This compromises the confidentiality and integrity of the publish service sessions, potentially allowing unauthorized data access or manipulation.
Mitigation Recommendations
Upgrade SiYuan to version 3.8.4 or later where this issue is fixed. The vulnerability is resolved by ensuring session cookies are properly secured and transmitted only over encrypted connections. Until upgraded, avoid using the publish service over unencrypted HTTP connections to reduce risk.
Technical Details
- Data Version
- 5.2
- Assigner Short Name
- VulnCheck
- Date Reserved
- 2026-09-26T02:31:42.100Z
- Cvss Version
- 4.0
- State
- PUBLISHED
Threat ID: 6ab7c9a5f7a7c5410652fd1e
Added to database: 09/26/2026, 13:33:25 UTC
Last enriched: 09/26/2026, 14:04:12 UTC
Last updated: 09/27/2026, 04:31:30 UTC
Views: 12
Community Reviews
0 reviewsCrowdsource mitigation strategies, share intel context, and vote on the most helpful responses. Sign in to add your voice and help keep defenders ahead.
Want to contribute mitigation steps or threat intel context? Sign in or create an account to join the community discussion.
Actions
Updates to AI analysis require Pro Console access. Upgrade inside Console → Billing.
Need more coverage?
Upgrade to Pro Console for AI refresh and higher limits.
For incident response and remediation, OffSeq services can help resolve threats faster.
Latest Threats
Check if your credentials are on the dark web
Instant breach scanning across billions of leaked records. Free tier available.