CVE-2026-84312: Nginx UI Casdoor SSO Callback Uses A Vulnerability

{
  "schema_version" : "1.4.0",
  "id" : "GHSA-44xr-mrhh-qm78",
  "modified" : "2026-10-15T20:12:52Z",
  "published" : "2026-10-15T20:12:52Z",
  "aliases" : [ "CVE-2026-84312" ],
  "summary" : "Nginx UI: Casdoor SSO callback uses a constant `state` parameter (login CSRF)",
  "details" : "## Summary\n\nIn the Casdoor SSO flow, the OAuth `state` parameter is hard-coded to `settings.CasdoorSettings.Application` — a value identical for every user and every login. The callback handler accepts whatever `state` the client sends without comparing it to anything stored in the user agent, enabling a login-CSRF: an attacker can force the victim's browser to authenticate as the *attacker*.\n\n## Details\n\n`api/user/casdoor.go:92-117` (`GetCasdoorUri`):\n\n```go\nfunc GetCasdoorUri(c *gin.Context) {\n    clientId := settings.CasdoorSettings.ClientId\n    redirectUri := settings.CasdoorSettings.RedirectUri\n    state := settings.CasdoorSettings.Application      // ← constant\n    ...\n    c.JSON(http.StatusOK, gin.H{\n        \"uri\": fmt.Sprintf(\n            \"%s/login/oauth/authorize?client_id=%s&response_type=code&redirect_uri=%s&state=%s&scope=read\",\n            endpoint, clientId, encodedRedirectUri, state),\n    })\n}\n```\n\n`api/user/casdoor.go:24-90` (`CasdoorCallback`):\n\n```go\ntype CasdoorLoginUser struct {\n    Code  string `json:\"code\" binding:\"required,max=255\"`\n    State string `json:\"state\" binding:\"required,max=255\"`\n}\n\nfunc CasdoorCallback(c *gin.Context) {\n    var loginUser CasdoorLoginUser\n    if !cosy.BindAndValid(c, &loginUser) { return }\n    ...\n    // state is NEVER compared to a per-session value\n    token, err := casdoorsdk.GetOAuthToken(loginUser.Code, loginUser.State)\n    ...\n    u, err := user.GetUser(claims.Name)        // username from Casdoor's JWT\n    ...\n    userToken, err := user.GenerateJWT(u)       // JWT minted for whatever user came back\n}\n```\n\nCompare with the OIDC implementation in `api/user/oidc.go:35-48`, which generates a random state, stores it in an `oidc_state` cookie, and validates it on the callback. Casdoor has no such check.\n\n## Proof of Concept\n\n1. Attacker initiates a Casdoor authorisation flow on their own browser, obtaining an authorisation `code` for *their* Casdoor account.\n2. Attacker hosts a page that auto-submits the captured `code` to the victim's nginx-ui:\n\n   ```html\n   <html><body><form action=\"https://victim.example/api/casdoor_callback\" method=\"POST\"\n                     enctype=\"text/plain\" id=\"x\">\n     <input name='{\"code\":\"<attacker_code>\",\"state\":\"<App>\",\"junk\":\"' value='\"}'>\n   </form>\n   <script>document.getElementById('x').submit()</script>\n   </body></html>\n   ```\n\n3. Server exchanges the attacker's `code`, looks up the username from `claims.Name` in the local user table, and mints a JWT for *that* row. The callback also sets the `_nginx_ui_secure_session` cookie via `middleware.EnsureSecureSessionCookie(c)` (`casdoor.go:84`) — meaning the victim is now silently authenticated as the attacker.\n4. Victim, believing they are using their own account, configures sites / TLS keys; the attacker reads them.\n\n## Impact\n\nLogin CSRF — the victim is forced to authenticate as the attacker, leading to data exfiltration of anything the victim subsequently uploads or configures. Particularly dangerous when nginx-ui is used by an organisation where Casdoor maps internal identities — the attacker can attribute their changes to the victim.\n\n## Patches\n\nMirror the OIDC implementation:\n\n```diff\n+ import (\n+    \"crypto/rand\"\n+    \"crypto/subtle\"\n+    \"encoding/hex\"\n+    ...\n+ )\n\n func GetCasdoorUri(c *gin.Context) {\n     ...\n-    state := settings.CasdoorSettings.Application\n+    b := make([]byte, 16)\n+    if _, err := rand.Read(b); err != nil {\n+        cosy.ErrHandler(c, err); return\n+    }\n+    state := hex.EncodeToString(b)\n+    c.SetSameSite(http.SameSiteLaxMode)\n+    c.SetCookie(\"casdoor_state\", state, 600, \"/\", \"\",\n+                cSettings.ServerSettings.EnableHTTPS, true)\n     ...\n }\n\n func CasdoorCallback(c *gin.Context) {\n+    expected, err := c.Cookie(\"casdoor_state\")\n+    if err != nil {\n+        c.AbortWithStatusJSON(http.StatusBadRequest,\n+            gin.H{\"message\":\"missing state cookie\"}); return\n+    }\n     var loginUser CasdoorLoginUser\n     if !cosy.BindAndValid(c, &loginUser) { return }\n+    if subtle.ConstantTimeCompare([]byte(expected), []byte(loginUser.State)) != 1 {\n+        c.AbortWithStatusJSON(http.StatusBadRequest,\n+            gin.H{\"message\":\"invalid state\"}); return\n+    }\n     ...\n }\n```\n\n## Workarounds\n\nDisable Casdoor SSO until patched. The OIDC integration in `api/user/oidc.go` is correctly implemented and can be used as a substitute.\n\n## References\n\n* [`api/user/casdoor.go:92-117`](https://github.com/0xJacky/nginx-ui/blob/dev/api/user/casdoor.go#L92-L117)\n* [`api/user/casdoor.go:24-90`](https://github.com/0xJacky/nginx-ui/blob/dev/api/user/casdoor.go#L24-L90)\n* [`api/user/oidc.go:35-48`](https://github.com/0xJacky/nginx-ui/blob/dev/api/user/oidc.go#L35-L48) (correct implementation for comparison)\n\n## Credits\n\nVishal Shukla ([@shukla304](https://github.com/shukla304)) and Sechub.dev AI Agent.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:L/A:N"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "Go",
      "name" : "Nginx-UI"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      } ]
    } ],
    "database_specific" : {
      "last_known_affected_version_range" : "< 1.9.10-0.20260703131214-23d1934099b0"
    }
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/0xJacky/nginx-ui/security/advisories/GHSA-44xr-mrhh-qm78"
  }, {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-84312"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/0xJacky/nginx-ui/commit/23d1934099b05b2a01589b48129dc3d3159d91c2"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/0xJacky/nginx-ui"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/0xJacky/nginx-ui/releases/tag/v2.4.1"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-287", "CWE-352" ],
    "severity" : "HIGH",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-10-15T20:12:52Z",
    "nvd_published_at" : "2026-10-12T22:17:05Z"
  }
}