CVE-2026-42183: Argo Workflows denial of service via nil pointer dereference in gatekeeper

CVE-2026-42183 · Severity: medium · CVSS 6.5 · Published 2026-05-09

Argo Workflows is an automation engine used to manage complex computing tasks on Kubernetes. A flaw in how the system handles user permissions for Single Sign-On (SSO) users can cause the server to crash when processing certain requests. This results in a denial of service, preventing affected users from accessing the platform or managing their workflows.

Technologies: Argo Project Argo Workflows, github.com/argoproj/argo-workflows (Go), github.com/argoproj/argo-workflows/v2 (Go), github.com/argoproj/argo-workflows/v3 (Go), github.com/argoproj/argo-workflows/v4 (Go). Vendors: Argo Project, Go.

Quick answers

Is CVE-2026-42183 exploited in the wild?
No. Junglewise Threat Intelligence has no report of CVE-2026-42183 being exploited in the wild.
How severe is CVE-2026-42183?
Medium severity, with a CVSS score of 6.5, published 9 May 2026.
Which products and versions are affected?
Argo Project Argo Workflows >= 4.0.0, <= 4.0.4, 4.0.0 to 4.0.4; Argo Project Workflows >= 4.0.0, < 4.0.5; github.com/argoproj/argo-workflows (Go) SEMVER:introduced=0; github.com/argoproj/argo-workflows/v2 (Go) SEMVER:introduced=0; and 2 more.
Is there a fix for CVE-2026-42183?
Yes. github.com/argoproj/argo-workflows/v4 (Go): upgrade to 4.0.5 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
How is CVE-2026-42183 attacked?
It is attacked over the network, in a software library.
Am I affected by CVE-2026-42183?
Check whether you run Argo Project Argo Workflows, Argo Project Workflows, github.com/argoproj/argo-workflows (Go) or one of the others listed at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

How to fix

  • github.com/argoproj/argo-workflows/v4 (Go): upgrade to 4.0.5 or later
    go get github.com/argoproj/argo-workflows/v4@v4.0.5

Technical details

A nil pointer dereference exists in `server/auth/gatekeeper.go` within the `rbacAuthorization()` function. When `SSO_DELEGATE_RBAC_TO_NAMESPACE=true` is configured, the system attempts to compare RBAC rule precedence between a namespace-level account and an SSO-level account. If a user's claims match a namespace-level rule but no SSO-namespace rule exists, the `loginAccount` variable remains nil, causing a panic when passed to the `precedence()` function which attempts to access its annotations. While the gRPC recovery interceptor prevents a full process crash, affected users receive HTTP 500 errors for all subsequent API requests, effectively resulting in a persistent denial of service for those identities. This issue is fixed in version 4.0.5.

Affected products

  • argoproj Argo Workflows >= 4.0.0, < 4.0.5

Identifiers

  • CVE-2026-42183
  • GHSA-p4gq-3vxj-f4jq
  • GO-2026-5527

Timeline

  • 2026-04-17: other: Vulnerability confirmed via PoC testing
  • 2026-04-23: patched: Version 4.0.5 released
  • 2026-05-09: disclosed: Advisory published

References

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