CVE-2026-42183Public exploitNetwork attack vector

Per-user API denial via nil account dereference

Published May 9, 2026 · Updated May 9, 2026

Denial of service in Argo Workflows 4.0.0 through 4.0.4 allows remote authenticated users to interrupt their own API access via SSO RBAC delegation. The rbacAuthorization function passes a nil loginAccount to precedence(), which unconditionally reads its Annotations after a namespace rule matches. Exploitation requires SSO namespace delegation, no matching SSO-namespace rule, and a matching namespace rule; recovery keeps the server running but every request from that user returns HTTP 500.

CVSS severity2.3
Low
EPSS probability0.38%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Denial of service in Argo Workflows 4.0.0 through 4.0.4 allows remote authenticated users to interrupt their own API access via SSO RBAC delegation. The rbacAuthorization function passes a nil loginAccount to precedence(), which unconditionally reads its Annotations after a namespace rule matches. Exploitation requires SSO namespace delegation, no matching SSO-namespace rule, and a matching namespace rule; recovery keeps the server running but every request from that user returns HTTP 500.

The record

CVE
CVE-2026-42183
Published
May 9, 2026
Updated
May 9, 2026
Vendor
Argo Project
Product
Argo Workflows
Classifications
CWE-476, T1499.004
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. May 9, 2026CVE publishedPublication date reported by the CVE source.
  2. May 9, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=>= 4.0.0, < 4.0.5

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

Argo Project · Argo Workflowsversion=>= 4.0.0, < 4.0.5

Published CVSS scores

6.5NIST NVDCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
2.3GitHub, Inc.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

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-476NULL Pointer Dereference
T1499.004Application or System Exploitation

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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