Nezha Monitoring: OAuth2 Redirect URL — Host Header Injection

CISA KEV is observed exploitation evidence. FIRST EPSS is a dated prediction of exploitation in the next 30 days. Missing scores are unknown. This collector requests predictions only for explicit CVE aliases in the public NuGet archive; Microsoft release views retain their existing prediction scope.

No collected risk observation for these identifiers. This does not establish absence of exploitation or a zero probability.

Nezha Monitoring is a self-hostable, lightweight, servers and websites monitoring and O&M tool. From version 1.0.0 to before version 2.2.0, the getRedirectURL function in oauth2.go:22-29 constructs the OAuth2 callback URL by concatenating the request's Host header with a fixed path, with zero validation of the Host header. This can result in host header injection. This issue has been patched in version 2.2.0.

Source published

12 Jun 2026 21:04:46 UTC

Source modified

15 Jun 2026 21:35:45 UTC

Observed here

23 Oct 2026 15:48:27 UTC

Source terms

CVE Program Terms of Use

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CVSS 3.1 · 6.8 CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:N

Nezha Monitoring is a self-hostable, lightweight, servers and websites monitoring and O&M tool. From version 1.0.0 to before version 2.2.0, the getRedirectURL function in oauth2.go:22-29 constructs the OAuth2 callback URL by concatenating the request's Host header with a fixed path, with zero validation of the Host header. This can result in host header injection. This issue has been patched in version 2.2.0.

Source published

Jun 12, 2026, 9:04:46 PM (timezone not stated)

Source modified

Jun 15, 2026, 9:35:45 PM (timezone not stated)

Observed here

7 Nov 2026 11:37:41 UTC

Source terms

ENISA EUVD · source terms and attribution apply

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This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: euvd · ENISA EUVD · source terms and attribution apply. Source text is retained; field grouping and change labels are provided by ChangeIntel.

EUVD CVSS 3.1 · 6.8 CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:N

Nezha Monitoring is a self-hostable, lightweight, servers and websites monitoring and O&M tool. From version 1.0.0 to before version 2.2.0, the getRedirectURL function in oauth2.go:22-29 constructs the OAuth2 callback URL by concatenating the request's Host header with a fixed path, with zero validation of the Host header. This can result in host header injection. This issue has been patched in version 2.2.0.

Source published

12 Jun 2026 22:16:52 UTC

Source modified

25 Oct 2026 23:10:00 UTC

Observed here

27 Oct 2026 14:13:22 UTC

Source terms

NIST NVD usage terms; underlying source attribution retained

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This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: nvd · NIST NVD usage terms; underlying source attribution retained. Source text is retained; field grouping and change labels are provided by ChangeIntel.

CVSS 3.1 · [email protected] · Secondary · 6.8 CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:N

## 1. Description The `getRedirectURL` function in `oauth2.go:22-29` constructs the OAuth2 callback URL by concatenating the request's `Host` header with a fixed path, with **zero validation** of the Host header: ```go func getRedirectURL(c *gin.Context) string { scheme := "http://" referer := c.Request.Referer() if forwardedProto := c.Request.Header.Get("X-Forwarded-Proto"); forwardedProto == "https" || strings.HasPrefix(referer, "https://") { scheme = "https://" } return scheme + c.Request.Host + "/api/v1/oauth2/callback" } ``` **File:** `cmd/dashboard/controller/oauth2.go:22-29` This function is called from `oauth2redirect()` at line 53: ```go func oauth2redirect(c *gin.Context) (*model.Oauth2LoginResponse, error) { // ... redirectURL := getRedirectURL(c) o2conf := o2confRaw.Setup(redirectURL) // ... url := o2conf.AuthCodeURL(state, oauth2.AccessTypeOnline) return &model.Oauth2LoginResponse{Redirect: url}, nil } ``` The `redirectURL` is passed into `o2confRaw.Setup(redirectURL)` which configures the OAuth2 `Config.RedirectURL` field (`oauth2config.go:22-33`). This `RedirectURL` is sent to the OAuth2 provider (e.g., GitHub, Google, Microsoft) as the callback endpoint. The OAuth2 provider will redirect the user's browser — along with the authorization code — to this URL after the user authenticates. The security issue is that `c.Request.Host` is directly user-controllable via the HTTP `Host` header. An attacker who can control which Host header reaches the oauth2redirect handler can: 1. Set `Host: evil.com` 2. `getRedirectURL` returns `https://evil.com/api/v1/oauth2/callback` 3. The OAuth2 provider redirects the victim's auth code to `evil.com` 4. The attacker's server at `evil.com` captures the auth code 5. The attacker exchanges the code for an access token, binding the victim's OAuth identity to the attacker's dashboard account The scheme detection (lines 24-27) uses `X-Forwarded-Proto` and the `Referer` header, both of which are also user-controllable in certain configurations, so the attacker can force `https://` scheme in the redirect URL. The `oauth2callback` handler at line 129 later uses `state.RedirectURL` (which is stored in `singleton.Cache` at line 65) when calling `exchangeOpenId` at line 152. The cached `redirectURL` was set during the initial `oauth2redirect` call, tying the attack flow together. ## 2. PoC A conceptual attack (no Docker needed): ``` Scenario: OAuth2 provider has loose redirect URI validation (e.g., allows wildcard subdomain matching) 1. Attacker crafts a URL to the dashboard's OAuth2 login endpoint with a modified Host header: GET /api/v1/oauth2/github HTTP/1.1 Host: attacker-controlled.com X-Forwarded-Proto: https 2. The dashboard responds with a redirect to: https://github.com/login/oauth/authorize?client_id=...&redirect_uri=https://attacker-controlled.com/api/v1/oauth2/callback&state=... 3. Victim clicks the attacker's link → authenticates with GitHub → GitHub redirects to https://attacker-controlled.com/api/v1/oauth2/callback?code=AUTH_CODE&state=... 4. Attacker captures the AUTH_CODE from their server logs 5. Attacker exchanges the code at the real dashboard's /api/v1/oauth2/callback endpoint (using the real Host header this time), binding the victim's OAuth identity to their dashboard account ``` **Prerequisites for full exploit:** - The victim must click the attacker's crafted link - The OAuth2 provider must accept the attacker's domain as a valid redirect URI (some providers accept `https://*/*` or allow wildcards; others are strict) ## 3. Impact - **Account takeover**: an attacker who intercepts the OAuth2 authorization code can bind the victim's OAuth identity (GitHub, Google, GitLab, etc.) to their own dashboard account, gaining the victim's access level and permissions - **Privilege escalation**: if the victim is an admin, the attacker gains full administrative control over the Nezha deployment — access to all servers, credentials, and configuration - **Persistence**: once bound, the attacker retains access even if the victim resets their password (unless they also unbind the OAuth2 identity) The attack complexity is higher than typical Host header injection scenarios because it requires: 1. The `Host` header to reach the dashboard's handler unmodified (bypassing reverse proxy normalization) 2. The OAuth2 provider to have loose redirect URL validation 3. User interaction (the victim must authenticate) However, the code-level vulnerability is unambiguous: the application trusts attacker-controlled input (`Host` header) for a security-critical URL that participates in the OAuth2 authorization code flow. ## 4. Remediation 1. **Validate the Host header** against a configured allowlist of known dashboard hostnames: ```go func getRedirectURL(c *gin.Context) string { host := c.Request.Host if !singleton.Conf.IsAllowedHost(host) { host = singleton.Conf.DashboardBaseURL // fallback } // ... } ``` 2. **Pin the redirect URL** to the configured dashboard URL from `singleton.Conf` instead of deriving it from the request Host header: ```go func getRedirectURL(c *gin.Context) string { return singleton.Conf.DashboardBaseURL + "/api/v1/oauth2/callback" } ``` 3. **Remove Host header-based URL construction** entirely — the OAuth2 redirect URL should be deterministic based on server configuration, not dynamic per-request 4. **Add Host header validation middleware** for all OAuth2-related endpoints as defense-in-depth

Source published

26 Jun 2026 23:05:19 UTC

Source modified

7 Jul 2026 16:11:15 UTC

Observed here

24 Oct 2026 13:19:41 UTC

Source terms

GitHub Advisory Database · CC-BY-4.0

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This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: osv · GitHub Advisory Database · CC-BY-4.0. Source text is retained; field grouping and change labels are provided by ChangeIntel.

CVSS_V3 · CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:N

Publisher rating · MODERATE

Nezha Monitoring: OAuth2 Redirect URL — Host Header Injection in github.com/nezhahq/nezha. NOTE: The source advisory for this report contains additional versions that could not be automatically mapped to standard Go module versions. (If this is causing false-positive reports from vulnerability scanners, please suggest an edit to the report.) The additional affected modules and versions are: github.com/nezhahq/nezha before v2.2.0.

Source published

7 Jul 2026 15:26:32 UTC

Source modified

7 Jul 2026 16:00:21 UTC

Observed here

24 Oct 2026 13:19:41 UTC

Source terms

OSV · upstream source license applies

Original source record · Cite this exact observation · Complete original publisher JSON

This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: osv · OSV · upstream source license applies. Source text is retained; field grouping and change labels are provided by ChangeIntel.