CVE-2026-101087: Nezha 2.0.10 through 2.3.2 SSRF Denylist Bypass IPv6

Vulnerability summary

CVE-2026-101087 is a medium (CVSS 5.3) Server-Side Request Forgery (SSRF) vulnerability in nezhahq nezha. EPSS estimates a 0.26% chance of exploitation in the next 30 days, higher than 16.8% of scored vulnerabilities.

Timeline

1. 27-09-2026
   PublishedVulnerability first disclosed.
2. 30-09-2026
   Last modifiedVulnerability information updated.

Description

Nezha versions 2.0.10 through 2.3.2 use a restricted HTTP client to validate user-configurable notification and DDNS webhook URLs, but the denylist did not cover IPv6 transition ranges — specifically the 6to4 prefix 2002::/16 and the local-use IPv4/IPv6 translation prefix 64:ff9b:1::/48. Because such addresses satisfy Go's netip.Addr.IsGlobalUnicast check, the URL validator accepted them. An authenticated user able to configure a webhook may be able to cause the dashboard to issue requests to an otherwise restricted IPv6 endpoint, but only where the dashboard's network provides unusual or non-standards-compliant routing for these transition ranges; no direct path to an IPv4 metadata, loopback, or private-network HTTP request has been demonstrated. The issue is fixed in version 2.3.3 (commit d1fcde8e), which blocks both prefixes.

• CWE-918Server-Side Request Forgery (SSRF)The web server receives a URL or similar request from an upstream component and retrieves the contents of this URL, but it does not sufficiently ensure that the request is being sent to the expected destination.