{
  "affected": [
    {
      "package": {
        "ecosystem": "Go",
        "name": "github.com/nezhahq/nezha"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "1.0.0"
            },
            {
              "fixed": "2.2.0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-53523"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-601"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-06-26T23:05:19Z",
    "nvd_published_at": "2026-06-12T22:16:52Z",
    "severity": "MODERATE"
  },
  "details": "## 1. Description\n\nThe `getRedirectURL` function in `oauth2.go:22-29` constructs the OAuth2 callback URL by concatenating the request\u0027s `Host` header with a fixed path, with **zero validation** of the Host header:\n\n```go\nfunc getRedirectURL(c *gin.Context) string {\n    scheme := \"http://\"\n    referer := c.Request.Referer()\n    if forwardedProto := c.Request.Header.Get(\"X-Forwarded-Proto\"); forwardedProto == \"https\" || strings.HasPrefix(referer, \"https://\") {\n        scheme = \"https://\"\n    }\n    return scheme + c.Request.Host + \"/api/v1/oauth2/callback\"\n}\n```\n\n**File:** `cmd/dashboard/controller/oauth2.go:22-29`\n\nThis function is called from `oauth2redirect()` at line 53:\n```go\nfunc oauth2redirect(c *gin.Context) (*model.Oauth2LoginResponse, error) {\n    // ...\n    redirectURL := getRedirectURL(c)\n    o2conf := o2confRaw.Setup(redirectURL)\n    // ...\n    url := o2conf.AuthCodeURL(state, oauth2.AccessTypeOnline)\n    return \u0026model.Oauth2LoginResponse{Redirect: url}, nil\n}\n```\n\nThe `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\u0027s browser \u2014 along with the authorization code \u2014 to this URL after the user authenticates.\n\nThe 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:\n\n1. Set `Host: evil.com`\n2. `getRedirectURL` returns `https://evil.com/api/v1/oauth2/callback`\n3. The OAuth2 provider redirects the victim\u0027s auth code to `evil.com`\n4. The attacker\u0027s server at `evil.com` captures the auth code\n5. The attacker exchanges the code for an access token, binding the victim\u0027s OAuth identity to the attacker\u0027s dashboard account\n\nThe 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.\n\nThe `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.\n\n## 2. PoC\n\nA conceptual attack (no Docker needed):\n\n```\nScenario: OAuth2 provider has loose redirect URI validation\n          (e.g., allows wildcard subdomain matching)\n\n1. Attacker crafts a URL to the dashboard\u0027s OAuth2 login endpoint\n   with a modified Host header:\n\n   GET /api/v1/oauth2/github HTTP/1.1\n   Host: attacker-controlled.com\n   X-Forwarded-Proto: https\n\n2. The dashboard responds with a redirect to:\n   https://github.com/login/oauth/authorize?client_id=...\u0026redirect_uri=https://attacker-controlled.com/api/v1/oauth2/callback\u0026state=...\n\n3. Victim clicks the attacker\u0027s link \u2192 authenticates with GitHub\n   \u2192 GitHub redirects to https://attacker-controlled.com/api/v1/oauth2/callback?code=AUTH_CODE\u0026state=...\n\n4. Attacker captures the AUTH_CODE from their server logs\n\n5. Attacker exchanges the code at the real dashboard\u0027s\n   /api/v1/oauth2/callback endpoint (using the real Host header\n   this time), binding the victim\u0027s OAuth identity to their\n   dashboard account\n```\n\n**Prerequisites for full exploit:**\n- The victim must click the attacker\u0027s crafted link\n- The OAuth2 provider must accept the attacker\u0027s domain as a valid redirect URI (some providers accept `https://*/*` or allow wildcards; others are strict)\n\n## 3. Impact\n\n- **Account takeover**: an attacker who intercepts the OAuth2 authorization code can bind the victim\u0027s OAuth identity (GitHub, Google, GitLab, etc.) to their own dashboard account, gaining the victim\u0027s access level and permissions\n- **Privilege escalation**: if the victim is an admin, the attacker gains full administrative control over the Nezha deployment \u2014 access to all servers, credentials, and configuration\n- **Persistence**: once bound, the attacker retains access even if the victim resets their password (unless they also unbind the OAuth2 identity)\n\nThe attack complexity is higher than typical Host header injection scenarios because it requires:\n1. The `Host` header to reach the dashboard\u0027s handler unmodified (bypassing reverse proxy normalization)\n2. The OAuth2 provider to have loose redirect URL validation\n3. User interaction (the victim must authenticate)\n\nHowever, 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.\n\n## 4. Remediation\n\n1. **Validate the Host header** against a configured allowlist of known dashboard hostnames:\n   ```go\n   func getRedirectURL(c *gin.Context) string {\n       host := c.Request.Host\n       if !singleton.Conf.IsAllowedHost(host) {\n           host = singleton.Conf.DashboardBaseURL // fallback\n       }\n       // ...\n   }\n   ```\n\n2. **Pin the redirect URL** to the configured dashboard URL from `singleton.Conf` instead of deriving it from the request Host header:\n   ```go\n   func getRedirectURL(c *gin.Context) string {\n       return singleton.Conf.DashboardBaseURL + \"/api/v1/oauth2/callback\"\n   }\n   ```\n\n3. **Remove Host header-based URL construction** entirely \u2014 the OAuth2 redirect URL should be deterministic based on server configuration, not dynamic per-request\n\n4. **Add Host header validation middleware** for all OAuth2-related endpoints as defense-in-depth",
  "id": "GHSA-9rc6-8cjv-rcvx",
  "modified": "2026-06-26T23:05:19Z",
  "published": "2026-06-26T23:05:19Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/nezhahq/nezha/security/advisories/GHSA-9rc6-8cjv-rcvx"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-53523"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/nezhahq/nezha"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:N",
      "type": "CVSS_V3"
    }
  ],
  "summary": "Nezha Monitoring: OAuth2 Redirect URL \u2014 Host Header Injection"
}