Argo Affected by SSO RBAC Delegation Nil Pointer Dereference DoS (gatekeeper.go)

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS 4.0

2.3 · 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 · score source

EPSS

• CVE-2026-42183: 0.38% estimated exploitation activity in the next 30 days; percentile 31.73 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

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 SSODELEGATERBACTONAMESPACE=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): 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 SSODELEGATERBACTONAMESPACE=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…

Published by the source

4 May 2026, 20:01 UTC

Last modified by the source

13 May 2026, 13:39 UTC

Source last checked

26 Oct 2026, 15:20 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-p4gq-3vxj-f4jq

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# Patch Next advisory brief: CVE-2026-42183

Advisory: Argo Affected by SSO RBAC Delegation Nil Pointer Dereference DoS (gatekeeper.go)
IDs: CVE-2026-42183, GHSA-p4gq-3vxj-f4jq
Record: https://patchnext.com/advisories/cve-2026-42183 (revision 1, source checked 26 Oct 2026, 15:20 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Low (CVSS 2.3)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: github.com/argoproj/argo-workflows/v4 4.0.5. A vendor fix does not mean a deployment is fixed.

## Affected components
- Go github.com/argoproj/argo-workflows/v4: affected >= 4.0.0, <= 4.0.4; fixed in 4.0.5

## Suggested inspection (read-only)
- Go github.com/argoproj/argo-workflows/v4: check the installed version with your package manager.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on github.com/argoproj/argo-workflows/v4.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-p4gq-3vxj-f4jq (GitHub-reviewed advisory GHSA-p4gq-3vxj-f4jq lists affected ranges: Go github.com/argoproj/argo-workflows/v4 >=4.0.0 <=4.0.4)

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