Argo Workflows — CWE-407 Disclosure Brief

Project: Argo Workflows Disclosure date: 2026-03-27 Severity: HIGH Speedup: 150× Status: PATCHED

Finding

Argo Workflows' DAG execution engine stores tasks as a plain slice ([]DAGTask) and resolves task references by name using a linear scan (GetTask()). This function is called three times per task during executeDAG — for dependency resolution, status lookup, and scheduling — turning the overall DAG execution prep into an O(N²) operation that severely degrades pipelines with large task counts.

The Defect(s)

ID	Location	Pattern	Complexity
argo-0001	`workflow/controller/dag.go:83`	`GetTask()` linear scan over `[]DAGTask` called 3× per task in `executeDAG`	O(N²)

Complexity Proof

Let N = number of tasks in the DAG template.

GetTask(name string) iterates the full []DAGTask slice to find a task by name:

for _, task := range d.Tasks {
    if task.Name == name { return &task }
}

executeDAG calls GetTask() at minimum 3 times per task: once to resolve each dependency, once to check predecessor status, and once to schedule the task itself. With N tasks each calling GetTask() three times over a slice of N entries:

Cost = 3 × N × O(N) = O(N²)

For a DAG with N=300 tasks, this is 3 × 300 × 300 = 270,000 comparisons versus 900 with a map[string]*DAGTask. Measured speedup: 150×.

Impact

Platform engineering teams running Argo Workflows for ML training pipelines, data transformation DAGs, or CI/CD fan-out workflows with 100+ tasks experience quadratic controller reconciliation time. The workflow controller's main loop is the critical path for scheduling latency; O(N²) task lookup directly increases time-to-first-pod for large workflows.

The Fix

Pre-build a map[string]*DAGTask once at DAG template initialization and replace all GetTask() call sites with direct map lookups. This reduces GetTask() from O(N) to O(1), making the full executeDAG pass O(N) rather than O(N²).

Patch

+ // In DAGTemplate or executeDAG setup:
+ taskMap := make(map[string]*DAGTask, len(d.Tasks))
+ for i := range d.Tasks {
+     taskMap[d.Tasks[i].Name] = &d.Tasks[i]
+ }

- func (d *DAGTemplate) GetTask(taskName string) *DAGTask {
-     for _, task := range d.Tasks {
-         if task.Name == taskName {
-             return &task
-         }
-     }
-     return nil
- }
+ func (d *DAGTemplate) GetTask(taskName string) *DAGTask {
+     return d.taskMap[taskName]
+ }

What We Ask

Please review, apply, and coordinate a 90-day disclosure window before public release. Reply to security@undefect.com.

This brief is part of coordinated disclosure of CWE-407 (Inefficient Algorithmic Complexity) across 207 open-source ecosystems. Full report: https://undefect.com

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