How severe is CVE-2025-21609?

CVE-2025-21609 has a CVSS 3.x base score of 9.1, rated critical severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity high, and availability high.

Is CVE-2025-21609 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (44th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2025-21609?

CVE-2025-21609 affects B3log Siyuan. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2025-21609?

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

Does CVE-2025-21609 have an EU (EUVD) identifier?

Yes. CVE-2025-21609 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2025-0017.

When was CVE-2025-21609 published?

CVE-2025-21609 was published on 2025-01-03 and last updated on 2026-06-17.

CVE-2025-21609

CVE-2025-21609 is a critical-severity vulnerability in B3log Siyuan with a CVSS 3.x base score of 9.1. 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-552.

Key facts

Severity: Critical (CVSS 3.x base score 9.1)
CVSS v4: 8.7
EPSS exploit prediction: 1% (44th percentile)
Actively exploited: Not listed in CISA KEV
EU (EUVD) id: EUVD-2025-0017
Weakness: CWE-552
Affected product: B3log Siyuan
Published: 2025-01-03
Last modified: 2026-06-17

Description

SiYuan is self-hosted, open source personal knowledge management software. SiYuan Note version 3.1.18 has an arbitrary file deletion vulnerability. The vulnerability exists in the `POST /api/history/getDocHistoryContent` endpoint. An attacker can craft a payload to exploit this vulnerability, resulting in the deletion of arbitrary files on the server. Commit d9887aeec1b27073bec66299a9a4181dc42969f3 fixes this vulnerability and is expected to be available in version 3.1.19.

Frequently asked questions

What is CVE-2025-21609?: SiYuan is self-hosted, open source personal knowledge management software. SiYuan Note version 3.1.18 has an arbitrary file deletion vulnerability. The vulnerability exists in the `POST /api/history/getDocHistoryContent` endpoint. An attacker can craft a payload to exploit this vulnerability, resulting in the deletion of arbitrary files on the server. Commit d9887aeec1b27073bec66299a9a4181dc42969f3 fixes this vulnerability and is expected to be available in version 3.1.19.
How severe is CVE-2025-21609?: CVE-2025-21609 has a CVSS 3.x base score of 9.1, rated critical severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity high, and availability high.
Is CVE-2025-21609 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (44th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2025-21609?: CVE-2025-21609 affects B3log Siyuan. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2025-21609?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its critical severity, prioritise patching exposed systems.
Does CVE-2025-21609 have an EU (EUVD) identifier?: Yes. CVE-2025-21609 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2025-0017.
When was CVE-2025-21609 published?: CVE-2025-21609 was published on 2025-01-03 and last updated on 2026-06-17.

References

Affected products (1)

cpe:2.3:a:b3log:siyuan:3.1.18:-:*:*:*:*:*:*

More vulnerabilities in B3log Siyuan

CVE-2026-32938 — Critical (CVSS 9.9): SiYuan is a personal knowledge management system. In versions 3.6.0 and below, the /api/lute/html2BlockDOM on the…
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