# 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

```diff
+ // 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.

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