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CVE-2026-33203

B3log Siyuan authentication bypass

7.5 HIGHPublic exploitEPSS 0.57%
  1. Published20 Mar 2026

Description

SiYuan is a personal knowledge management system. Prior to version 3.6.2, the SiYuan kernel WebSocket server accepts unauthenticated connections when a specific "auth keepalive" query parameter is present. After connection, incoming messages are parsed using unchecked type assertions on attacker-controlled JSON. A remote attacker can send malformed messages that trigger a runtime panic, potentially crashing the kernel process and causing denial of service. Version 3.6.2 fixes the issue.

CVSS 3.1 breakdown

Attack vectorNetwork
Attack complexityLow
Privileges requiredNone
User interactionNone
ScopeUnchanged
ConfidentialityNone
IntegrityNone
AvailabilityHigh
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Affected products

B3log Siyuan< 3.6.2

Remediation

Fixed in
B3log Siyuan≥ 3.6.2

References

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Frequently asked

Is CVE-2026-33203 being actively exploited?

CVE-2026-33203 is not in the CISA KEV catalog. A public exploit reference exists, so treat it as exploitable. Its EPSS exploit probability is 0.57%.

How severe is CVE-2026-33203?

CVE-2026-33203 has a CVSS 3.1 base score of 7.5, rated high. EPSS estimates a 0.57% probability of exploitation.

Which products are affected by CVE-2026-33203?

Affected products include B3log Siyuan.

How do I fix CVE-2026-33203?

Upgrade affected software to a fixed version, for example B3log Siyuan 3.6.2 or later, then confirm no affected versions remain in your inventory.

How Secuno handles this

Secuno correlates vulnerabilities like CVE-2026-33203 against the real software inventory on every managed device, as each hourly inventory arrives. Rather than a static severity, each match is scored in context: exploit availability, EPSS, the asset's exposure, and business criticality decide where it lands in the queue. If an affected version is present anywhere across your portfolio, it surfaces automatically with a prioritised remediation path.

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Data from the NVD, CISA KEV catalog and FIRST EPSS. CVSS 3.1 base score shown where available.