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CVE-2026-40886: Argo Workflows: Unchecked annotation parsing in pod informer crashes Argo Workflows controller

• Severity: high (CVSS 7.7 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.4% probability of exploitation in the next 30 days
• Public exploit or detection template: yes
• Published: 2026-04-23 · updated 2026-10-26
• Weakness: CWE-129

Description

Argo Workflows is an open source container-native workflow engine for orchestrating parallel jobs on Kubernetes. From 3.6.5 to 4.0.4, an unchecked array index in the pod informer's podGCFromPod() function causes a controller-wide panic when a workflow pod carries a malformed workflows.argoproj.io/pod-gc-strategy annotation. Because the panic occurs inside an informer goroutine (outside the controller's recover() scope), it crashes the entire controller process. The poisoned pod persists across restarts, causing a crash loop that halts all workflow processing until the pod is manually deleted. This vulnerability is fixed in 4.0.5 and 3.7.14.

Affected products

• argoproj argo-workflows: from 3.6.5 through 3.6.19; from 3.7.0 before 3.7.14; from 4.0.0 before 4.0.5 — fixed in 3.7.14, 4.0.5

How to fix

Upgrade to a fixed version: argoproj argo-workflows 3.7.14, 4.0.5. Check the vendor advisory for mitigations.

References

• https://github.com/argoproj/argo-workflows/security/advisories/GHSA-5jv8-h7qh-rf5p
• https://access.redhat.com/security/cve/CVE-2026-40886
• https://bugzilla.redhat.com/show_bug.cgi?id=2461236
• https://github.com/argoproj/argo-workflows/security/advisories/GHSA-5jv8-h7qh-rf5p
• https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-40886.json

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