{"id":"GHSA-p4gq-3vxj-f4jq","summary":"Argo Affected by SSO RBAC Delegation Nil Pointer Dereference DoS (gatekeeper.go)","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` — 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'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.\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).","aliases":["BIT-argo-workflows-2026-42183","CVE-2026-42183","GO-2026-5527"],"modified":"2026-07-17T21:06:58.414146158Z","published":"2026-05-04T20:01:13Z","database_specific":{"severity":"LOW","github_reviewed":true,"github_reviewed_at":"2026-05-04T20:01:13Z","nvd_published_at":"2026-05-09T04:16:23Z","cwe_ids":["CWE-476"]},"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"}],"affected":[{"package":{"name":"github.com/argoproj/argo-workflows/v4","ecosystem":"Go","purl":"pkg:golang/github.com/argoproj/argo-workflows/v4"},"ranges":[{"type":"SEMVER","events":[{"introduced":"4.0.0"},{"fixed":"4.0.5"}]}],"database_specific":{"last_known_affected_version_range":"\u003c= 4.0.4","source":"https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/05/GHSA-p4gq-3vxj-f4jq/GHSA-p4gq-3vxj-f4jq.json"}}],"schema_version":"1.9.0","severity":[{"type":"CVSS_V4","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"}]}