InvalidUserID.Malformed
AWS InvalidUserID.Malformed means owner or executableBy identifiers in EC2 describe requests are invalid. In Amazon EC2, this error returns HTTP 400.
Last reviewed: February 13, 2026|Editorial standard: source-backed technical guidance
What Does Invalid User ID Malformed Mean?
EC2 rejects owner-context filters before resource evaluation, so image and snapshot discovery workflows fail until identity parameters are provided in valid account-ID form.
Common Causes
- -Owner or executableBy values are not valid AWS account identifiers for EC2 describe calls.
- -Automation passes canonical user IDs or malformed strings where 12-digit account IDs are required.
- -Input lists include whitespace, delimiters, or casing issues that break query validation.
- -Cross-account datasets inject IDs from the wrong partition or decommissioned account maps.
How to Fix Invalid User ID Malformed
- 1Validate owner and executableBy values against supported EC2 identifier formats before call dispatch.
- 2Use 12-digit account IDs or supported keywords where the API allows them, not free-form principal strings.
- 3Normalize and sanitize list inputs (trim, dedupe, strip invalid separators) before signing requests.
- 4Re-run DescribeImages or DescribeSnapshots with corrected identity filters.
Step-by-Step Diagnosis for Invalid User ID Malformed
- 1Capture request ID plus the exact owner/executableBy filter payload sent on the wire.
- 2Trace identity-filter values through IaC variables, CLI args, and runtime config rendering.
- 3Compare failing filter sets with a known-good DescribeImages/DescribeSnapshots invocation.
- 4Verify account-map sources for partition, formatting, and stale-account drift.
Owner and ExecutableBy Filter Validation
- -Validate each filter value against EC2 owner/executableBy expectations (example: string label passed instead of 12-digit account ID).
- -Inspect partition and account-map alignment before replay (example: commercial account IDs reused in GovCloud automation path).
Query Payload Hygiene Audit
- -Audit filter list serialization for whitespace and delimiter defects (example: comma-separated string is emitted as one malformed token).
- -Trace stale identifier injection from config templates (example: deprecated environment owner list remains in rendered request payload).
How to Verify the Fix
- -Replay the same EC2 describe call and confirm InvalidUserID.Malformed is cleared.
- -Validate owner/executableBy filters now return expected image or snapshot sets.
- -Confirm logs no longer show malformed identity-filter tokens for this workflow.
How to Prevent Recurrence
- -Centralize owner/executableBy identifier generation in one validated utility.
- -Add CI checks that enforce EC2 filter format rules for account identifiers.
- -Continuously reconcile account maps against Organizations inventory and partition boundaries.
Pro Tip
- -persist both raw and normalized identity-filter payloads in debug logs to pinpoint malformed token insertion layers quickly.
Decision Support
Compare Guide
HTTP 400 vs 422: Bad Request vs Unprocessable Content
Fix API payload issues faster by using 400 for malformed syntax and 422 for semantic validation failures, so clients correct format before business rules.
Playbook
CORS Error Fix Playbook (Preflight / Origin / Credentials)
Use this playbook to separate browser-enforced cross-origin policy failures from server-side CORS header and route defects and apply strict origin and credential controls safely.
Playbook
Validation Failure Playbook (400 / 422 / INVALID_ARGUMENT)
Use this playbook to separate malformed-request failures from semantic validation failures, then fix request contracts without broad server-side bypasses.
Official References
Provider Context
This guidance is specific to AWS services. Always validate implementation details against official provider documentation before deploying to production.