GHSA-P4GQ-3VXJ-F4JQ

Vulnerability from github – Published: 2026-05-04 20:01 – Updated: 2026-05-13 13:39
VLAI
Summary
Argo Affected by SSO RBAC Delegation Nil Pointer Dereference DoS (gatekeeper.go)
Details

Summary

A nil pointer dereference in server/auth/gatekeeper.go rbacAuthorization() causes a panic (denial of service) for SSO users whose claims match a namespace-level RBAC rule but not an SSO-namespace rule, when SSO_DELEGATE_RBAC_TO_NAMESPACE=true.

Details

When getServiceAccount(claims, ssoNamespace) returns nil (no matching rule), the error is suppressed and loginAccount remains nil. If RBAC delegation finds a matching namespaceAccount, line 304 calls precedence(loginAccount) which unconditionally accesses serviceAccount.Annotations — nil pointer dereference.

Affected code (v4.0.4):

// gatekeeper.go:304
} else if precedence(namespaceAccount) > precedence(loginAccount) {
    // loginAccount is nil here -> precedence(nil) -> PANIC

// gatekeeper.go:232-234
func precedence(serviceAccount *corev1.ServiceAccount) int {
    i, _ := strconv.Atoi(serviceAccount.Annotations[common.AnnotationKeyRBACRulePrecedence])
    return i
}

PoC

Live-tested 2026-04-17: kind cluster, Argo Workflows v4.0.4, Dex v2.43.1 OIDC provider.

  1. Deploy Argo Workflows with --auth-mode=sso --auth-mode=client, SSO pointing to Dex, RBAC enabled.
  2. Set SSO_DELEGATE_RBAC_TO_NAMESPACE=true on the argo-server deployment.
  3. Create an RBAC ServiceAccount with workflows.argoproj.io/rbac-rule: "true" annotation in a target namespace (e.g., target-ns).
  4. Do not create a matching RBAC rule in the SSO namespace (argo).
  5. Authenticate via the Dex SSO flow.
  6. Request GET /api/v1/workflows/target-ns with the SSO session cookie.
  7. Server returns HTTP 500: {"code":13,"message":"runtime error: invalid memory address or nil pointer dereference"}
  8. Server logs: Recovered from panic with stack trace at gatekeeper.go:233 (precedence()) called from gatekeeper.go:304.

Every subsequent API request from affected SSO users triggers the same panic.

Impact

Permanent denial of service for any SSO user whose claims don't match SSO-namespace RBAC but do match a target namespace rule. Realistic in multi-tenant deployments with per-namespace RBAC. The gRPC recovery interceptor catches the panic so the server process survives, but the affected user gets HTTP 500 on every request.

Suggested Fix

Add nil check: if loginAccount == nil || precedence(namespaceAccount) > precedence(loginAccount)

AI Disclosure

This advisory was prepared with AI assistance (Claude Code, Anthropic).

Severity
2.3 (Low)
CVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N
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{
  "affected": [
    {
      "database_specific": {
        "last_known_affected_version_range": "\u003c= 4.0.4"
      },
      "package": {
        "ecosystem": "Go",
        "name": "github.com/argoproj/argo-workflows/v4"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "4.0.0"
            },
            {
              "fixed": "4.0.5"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-42183"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-476"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-05-04T20:01:13Z",
    "nvd_published_at": "2026-05-09T04:16:23Z",
    "severity": "LOW"
  },
  "details": "### Summary\nA nil pointer dereference in `server/auth/gatekeeper.go` `rbacAuthorization()` causes a panic (denial of service) for SSO users whose claims match a namespace-level RBAC rule but not an SSO-namespace rule, when `SSO_DELEGATE_RBAC_TO_NAMESPACE=true`.\n\n### Details\nWhen `getServiceAccount(claims, ssoNamespace)` returns nil (no matching rule), the error is suppressed and `loginAccount` remains nil. If RBAC delegation finds a matching `namespaceAccount`, line 304 calls `precedence(loginAccount)` which unconditionally accesses `serviceAccount.Annotations` \u2014 nil pointer dereference.\n\n**Affected code (v4.0.4):**\n\n```go\n// gatekeeper.go:304\n} else if precedence(namespaceAccount) \u003e precedence(loginAccount) {\n    // loginAccount is nil here -\u003e precedence(nil) -\u003e PANIC\n\n// gatekeeper.go:232-234\nfunc precedence(serviceAccount *corev1.ServiceAccount) int {\n    i, _ := strconv.Atoi(serviceAccount.Annotations[common.AnnotationKeyRBACRulePrecedence])\n    return i\n}\n```\n\n### PoC\n**Live-tested 2026-04-17:** kind cluster, Argo Workflows v4.0.4, Dex v2.43.1 OIDC provider.\n\n1. Deploy Argo Workflows with `--auth-mode=sso --auth-mode=client`, SSO pointing to Dex, RBAC enabled.\n2. Set `SSO_DELEGATE_RBAC_TO_NAMESPACE=true` on the argo-server deployment.\n3. Create an RBAC ServiceAccount with `workflows.argoproj.io/rbac-rule: \"true\"` annotation in a target namespace (e.g., `target-ns`).\n4. Do **not** create a matching RBAC rule in the SSO namespace (`argo`).\n5. Authenticate via the Dex SSO flow.\n6. Request `GET /api/v1/workflows/target-ns` with the SSO session cookie.\n7. Server returns HTTP 500: `{\"code\":13,\"message\":\"runtime error: invalid memory address or nil pointer dereference\"}`\n8. Server logs: `Recovered from panic` with stack trace at `gatekeeper.go:233` (`precedence()`) called from `gatekeeper.go:304`.\n\nEvery subsequent API request from affected SSO users triggers the same panic.\n\n### Impact\nPermanent denial of service for any SSO user whose claims don\u0027t match SSO-namespace RBAC but do match a target namespace rule. Realistic in multi-tenant deployments with per-namespace RBAC. The gRPC recovery interceptor catches the panic so the server process survives, but the affected user gets HTTP 500 on every request.\n\n### Suggested Fix\nAdd nil check: `if loginAccount == nil || precedence(namespaceAccount) \u003e precedence(loginAccount)`\n\n### AI Disclosure\nThis advisory was prepared with AI assistance (Claude Code, Anthropic).",
  "id": "GHSA-p4gq-3vxj-f4jq",
  "modified": "2026-05-13T13:39:11Z",
  "published": "2026-05-04T20:01:13Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/argoproj/argo-workflows/security/advisories/GHSA-p4gq-3vxj-f4jq"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-42183"
    },
    {
      "type": "WEB",
      "url": "https://github.com/argoproj/argo-workflows/commit/c4cc17d0c034fa9a9cc01ef1af6c8016c93071d4"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/argoproj/argo-workflows"
    },
    {
      "type": "WEB",
      "url": "https://github.com/argoproj/argo-workflows/releases/tag/v4.0.5"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N",
      "type": "CVSS_V4"
    }
  ],
  "summary": "Argo Affected by SSO RBAC Delegation Nil Pointer Dereference DoS (gatekeeper.go)"
}


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