How severe is CVE-2026-33203?

CVE-2026-33203 has a CVSS 3.x base score of 7.5, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability high.

Is CVE-2026-33203 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (39th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2026-33203?

CVE-2026-33203 affects B3log Siyuan. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2026-33203?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.

Does CVE-2026-33203 have an EU (EUVD) identifier?

Yes. CVE-2026-33203 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-13869.

When was CVE-2026-33203 published?

CVE-2026-33203 was published on 2026-03-20 and last updated on 2026-06-17.

CVE-2026-33203

CVE-2026-33203 is a high-severity vulnerability in B3log Siyuan with a CVSS 3.x base score of 7.5. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-248.

Key facts

Severity: High (CVSS 3.x base score 7.5)
EPSS exploit prediction: 0% (39th percentile)
Actively exploited: Not listed in CISA KEV
EU (EUVD) id: EUVD-2026-13869
Weakness: CWE-248
Affected product: B3log Siyuan
Published: 2026-03-20
Last modified: 2026-06-17

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.

Frequently asked questions

What is CVE-2026-33203?: 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.
How severe is CVE-2026-33203?: CVE-2026-33203 has a CVSS 3.x base score of 7.5, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability high.
Is CVE-2026-33203 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (39th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2026-33203?: CVE-2026-33203 affects B3log Siyuan. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2026-33203?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.
Does CVE-2026-33203 have an EU (EUVD) identifier?: Yes. CVE-2026-33203 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-13869.
When was CVE-2026-33203 published?: CVE-2026-33203 was published on 2026-03-20 and last updated on 2026-06-17.

References

https://github.com/siyuan-note/siyuan/security/advisories/GHSA-3g9h-9hp4-654v

Affected products (1)

cpe:2.3:a:b3log:siyuan:*:*:*:*:*:*:*:*

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