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Nezha CVE-2026-101090

| EUVDEUVD-2026-88025 CRITICAL
URL Redirection to Untrusted Site (Open Redirect) (CWE-601)
2026-09-27 VulnCheck GHSA-62gj-x2f3-j2wj
9.3
CVSS 4.0 · Vendor: VulnCheck
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Severity by source

Vendor (VulnCheck) PRIMARY
9.3 CRITICAL
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
vuln.today AI
6.8 MEDIUM

AC:H and UI:R because success needs a permissive IdP redirect policy plus a victim induced to start login; PR:N (pre-auth); C:H/I:H for account takeover, A:N as no availability loss.

3.1 AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:N
4.0 AV:N/AC:H/AT:P/PR:N/UI:P/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N

Primary rating from Vendor (VulnCheck).

CVSS VectorVendor: VulnCheck

Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
None
Scope
X

Lifecycle Timeline

4
POC Analysis Generated
Sep 27, 2026 - 23:20 vuln.today
Metadata Corrected
Sep 27, 2026 - 21:40 vuln.today
tag: Go added
Analysis Generated
Sep 27, 2026 - 21:21 vuln.today
CVE Published
Sep 27, 2026 - 20:50 cve.org
CRITICAL 9.3

DescriptionCVE.org

Nezha 2.2.3 contains a Host header injection regression in the OAuth2 redirect endpoint. When the new optional dashboard_host setting is empty, /api/v1/oauth2/{provider} (cmd/dashboard/controller/oauth2.go) reflects the attacker-supplied HTTP Host header into the redirect_uri sent to the identity provider instead of falling back to the configured install_host. An attacker who induces a victim to begin OAuth2 login via a request that reaches Nezha with a forged Host header can cause an attacker-controlled callback URL to be used as the redirect_uri; if the OAuth2 provider accepts it, the victim's authorization code is delivered to the attacker origin, allowing the attacker to complete the OAuth2 login/binding flow and take over the account. This regresses the fix for GHSA-9rc6-8cjv-rcvx and is configuration-dependent (dashboard_host empty). At the time of the advisory no patched version was available.

AnalysisAI

Host header injection in Nezha 2.2.3's OAuth2 redirect endpoint (/api/v1/oauth2/{provider}) allows an unauthenticated remote attacker who can control the HTTP Host header on a request reaching the server to make Nezha emit an attacker-chosen redirect_uri to the configured identity provider; a victim induced to start the OAuth2 login/binding flow can then have their authorization code delivered to the attacker's origin, letting the attacker complete the flow and take over the account. The bug is a regression of the GHSA-9rc6-8cjv-rcvx fix and only manifests when the new optional dashboard_host setting is left empty, so the code no longer falls back to install_host; exploitation also requires victim interaction and an identity provider that accepts the forged redirect URI, which is why the independent assessment scores it CVSS:3.1/AV:N/AC:H/PR:N/UI:R while the vendor-style CVSS 4.0 rating is 9.3. …

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Attack ChainAIDerived

Hypothetical attack flow derived from CVE metadata

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Vulnerability AssessmentAI

Exploitation Requires ALL of: (1) the Nezha instance is configured for OAuth2 login AND the new optional dashboard_host setting is left EMPTY (the fallback to install_host only fires when dashboard_host is non-empty) - this is the core regression condition; (2) the deployment reaches Nezha with an attacker-controllable HTTP Host header (e.g. … Additional conditions and limiting factors are described in the full assessment.
Risk Assessment This is a genuine but conditional account-takeover vulnerability, not a slam-dunk critical. … Full risk analysis with EPSS, KEV, and SSVC signal comparison available after sign-in.
Exploit Scenario Full exploit scenario with step-by-step reproduction available after sign-in.
Remediation No vendor-released patched version was published with the advisory, so the primary action is to apply the upstream fix commit 38824dbc11a63964c5b9296ae4c68e62b34fa04b (or later) or wait for a tagged release that contains it, tracked via GHSA-rf68-8gjr-36q7. … Detailed patch versions, workarounds, and compensating controls in full report.

Recommended ActionAI

Within 24 hours, ensure the Nezha dashboard_host configuration setting is explicitly set to the correct external hostname to prevent the empty fallback, and validate Host headers at the reverse proxy to reject untrusted values. …

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CVE-2026-101090 vulnerability details – vuln.today

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