PatchSiren cyber security CVE debrief

CVE-2026-53521 nezhahq CVE debrief

Nezha Monitoring is a self-hostable, lightweight tool for monitoring servers and websites. A vulnerability exists in versions 2.0.14 to before 2.1.0, where the PATCH /server/{id} endpoint accepts and persists nonexistent ddns_profiles IDs for a member-owned server. If another user later creates a DDNS profile with one of those IDs, the DDNS worker resolves the stored ID and dispatches an update using the other user's DDNS profile configuration in the context of the attacker's server. This issue has been patched in version 2.1.0.

Vendor: nezhahq
Product: nezha
CVSS: MEDIUM 6.4
CISA KEV: Not listed in stored evidence
Original CVE published: 2026-06-12
Original CVE updated: 2026-06-12
Advisory published: 2026-06-12
Advisory updated: 2026-06-12

Who should care

Users of Nezha Monitoring, particularly those who have not upgraded to version 2.1.0, should be aware of this vulnerability and take necessary precautions.

Technical summary

The vulnerability exists in the PATCH /server/{id} endpoint of Nezha Monitoring, where it accepts and persists nonexistent ddns_profiles IDs for a member-owned server. This allows an attacker to potentially dispatch an update using another user's DDNS profile configuration.

Defensive priority

MEDIUM

Recommended defensive actions

Upgrade to Nezha Monitoring version 2.1.0 or later.
Review and restrict access to the PATCH /server/{id} endpoint.
Monitor for suspicious activity related to DDNS profile updates.

Evidence notes

The CVE-2026-53521 vulnerability has a CVSS score of 6.4 and is classified as MEDIUM severity. The vulnerability was published on 2026-06-12T22:16:52.230Z and has not been modified since.

Official resources

CVE-2026-53521 was published on 2026-06-12T22:16:52.230Z.