How severe is CVE-2026-42183?

No CVSS score has been assigned to CVE-2026-42183 yet. Review the advisory details and affected package list to assess your exposure.

Which packages are affected by CVE-2026-42183?

CVE-2026-42183 affects the following packages: github.com/argoproj/argo-workflows/v4 (Go). Ecosystems affected: Go.

How do I fix CVE-2026-42183?

Update github.com/argoproj/argo-workflows/v4 to 4.0.5 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-42183 is resolved across your whole dependency graph.

How do I detect CVE-2026-42183 in my Go dependencies?

Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for github.com/argoproj/argo-workflows/v4, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

How do I mitigate CVE-2026-42183 if there is no patch (or I can't update yet)?

Cap what an attacker can consume: apply request size, rate and timeout limits in front of the affected component, and run it with memory and CPU limits so exhaustion degrades one worker rather than the whole service.

Is CVE-2026-42183 actively exploited in the wild?

No public exploit code has been indexed for CVE-2026-42183 yet. This does not mean the vulnerability cannot be exploited — absence of public exploits does not imply safety. Apply the recommended fix and use O3 Security to monitor your exposure.

What is the EPSS score for CVE-2026-42183?

CVE-2026-42183 has an EPSS (Exploit Prediction Scoring System) score of 0.4%, placing it in the 32th percentile of all CVEs. EPSS is maintained by FIRST.org and estimates the probability that a vulnerability will be exploited in the wild within the next 30 days. This score indicates relatively lower exploitation probability, though the CVSS severity should still guide your patching priority.

What type of vulnerability is CVE-2026-42183?

CVE-2026-42183 is classified as NULL Pointer Dereference (CWE-476). This weakness type describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation.

When was CVE-2026-42183 published, and has it been updated?

CVE-2026-42183 was published on May 9, 2026 and was last updated on October 28, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

🐹 Go

Not in CISA KEV

CVE-2026-42183 — argo-workflows

Fix: argoproj/argo-workflows@c4cc17d

CVE-2026-42183 is a NULL Pointer Dereference vulnerability in github.com/argoproj/argo-workflows/v4. A fix is available for github.com/argoproj/argo-workflows/v4 — see the affected versions and patch details below.

Argo Workflows: SSO RBAC Delegation Nil Pointer Dereference DoS (gatekeeper.go)

Also known asBIT-argo-workflows-2026-42183GHSA-p4gq-3vxj-f4jqGO-2026-5527

Published

May 9, 2026

Updated

Oct 28, 2026

Affected

1 pkg

Patched

1 / 1

Exploits

None indexed

Exploitation data as of Nov 9, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

Exploitation Status

No confirmed exploitation observed yet

CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.

Exploitation and automatability from CISA’s SSVC triage for CVE-2026-42183.

EPSS Exploitation Probability

via FIRST.org ↗

0.4%probability of exploitation in next 30 days

Lower Risk0.00%

Lower risk than most CVEs32th percentile — riskier than 32% of all scored CVEsHighest risk

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

Real-World Exposure

1 pkg affected

🐹github.com/argoproj/argo-workflows/v4

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects Go packages — download data is not available via public APIs for these ecosystems.

Description

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.

Deploy Argo Workflows with --auth-mode=sso --auth-mode=client, SSO pointing to Dex, RBAC enabled.
Set SSO_DELEGATE_RBAC_TO_NAMESPACE=true on the argo-server deployment.
Create an RBAC ServiceAccount with workflows.argoproj.io/rbac-rule: "true" annotation in a target namespace (e.g., target-ns).
Do not create a matching RBAC rule in the SSO namespace (argo).
Authenticate via the Dex SSO flow.
Request GET /api/v1/workflows/target-ns with the SSO session cookie.
Server returns HTTP 500: {"code":13,"message":"runtime error: invalid memory address or nil pointer dereference"}
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).

Affected Packages

1 total 1 fixed

Ecosystem	Package	Vulnerable range	Fix
🐹Go	`github.com/argoproj/argo-workflows/v4`	≥ 4.0.0&&< 4.0.5	4.0.5`go get github.com/argoproj/argo-workflows/v4@v4.0.5`

Affected Products

1 product · 1 configurations

Application

argo workflowsargoproj

≥ 4.0.0 && < 4.0.5

range

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for github.com/argoproj/argo-workflows/v4, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update github.com/argoproj/argo-workflows/v4 to 4.0.5 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-42183 is resolved across your whole dependency graph.
Workarounds
Cap what an attacker can consume: apply request size, rate and timeout limits in front of the affected component, and run it with memory and CPU limits so exhaustion degrades one worker rather than the whole service.

Fixing This On Your OS

If you run this on a Linux distribution, patch through your package manager against the distro's own security advisory below — it tracks the exact backported fix for your release, which can ship on a different timeline (and sometimes a different severity) than the upstream project.

Red HatModerate

Workaround published by Red Hat

To mitigate this issue, disable the `SSO_DELEGATE_RBAC_TO_NAMESPACE` feature if it is not required for your deployment. This will prevent the vulnerable code path from being exercised. Disabling this feature may affect how RBAC is delegated to namespaces for SSO users. A restart of the Argo Workflows service may be required for the change to take effect.

Source: Red Hat security advisory for CVE-2026-42183 (CC BY 4.0)

Frequently Asked Questions

### 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. **Af