{"id":"CVE-2026-42183","aliases":["BIT-argo-workflows-2026-42183","GHSA-p4gq-3vxj-f4jq","GO-2026-5527"],"url":"https://o3.security/vulnerability/CVE-2026-42183","summary":"Argo Workflows: 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) > precedence(loginAccount) {\n    // loginAccount is nil here -> precedence(nil) -> 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) > precedence(loginAccount)`\n\n### AI Disclosure\nThis advisory was prepared with AI assistance (Claude Code, Anthropic).","published":"2026-05-09T03:44:10.712Z","modified":"2026-08-12T03:51:35.223193513Z","cvss":null,"epss":{"score":0.00377,"percentile":0.30715,"asOf":"2026-08-14"},"cisaKev":null,"exploitsKnown":0,"affectedPackages":[{"ecosystem":"Go","name":"github.com/argoproj/argo-workflows/v4","fixedVersion":"4.0.5"}],"fix":{"url":"https://github.com/argoproj/argo-workflows/commit/c4cc17d0c034fa9a9cc01ef1af6c8016c93071d4","label":"argoproj/argo-workflows@c4cc17d"},"references":[{"type":"WEB","url":"https://github.com/argoproj/argo-workflows/releases/tag/v4.0.5"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/42xxx/CVE-2026-42183.json"},{"type":"ADVISORY","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":"FIX","url":"https://github.com/argoproj/argo-workflows/commit/c4cc17d0c034fa9a9cc01ef1af6c8016c93071d4"},{"type":"PACKAGE","url":"https://github.com/argoproj/argo-workflows"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-08-12T03:51:35.223193513Z"}}