CVE-2026-40886: argoproj argo_workflows Improper Validation of Array Index

Vulnerability summary

CVE-2026-40886 is a high (CVSS 7.7) Improper Validation of Array Index vulnerability in argoproj argo_workflows. EPSS estimates a 0.59% chance of exploitation in the next 30 days, higher than 47.2% of scored vulnerabilities. 1 public exploit is recorded.

Timeline

1. 23-04-2026
   PublishedVulnerability first disclosed.
2. 15-07-2026
   Last modifiedVulnerability information updated.

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.

• CWE-129Improper Validation of Array IndexThe product uses untrusted input when calculating or using an array index, but the product does not validate or incorrectly validates the index to ensure the index references a valid position within the array.
• CWE-1285Improper Validation of Specified Index, Position, or Offset in InputThe product receives input that is expected to specify an index, position, or offset into an indexable resource such as a buffer or file, but it does not validate or incorrectly validates that the specified index/position/offset has the required properties.