Executive Advisory Summary

Amazon Web Services (AWS) has published a critical security bulletin detailing CVE-2026-62210, an authentication validation vulnerability in the inbound System for Cross-domain Identity Management (SCIM 2.0) listener of AWS IAM Identity Center (formerly AWS Single Sign-On). The vulnerability allowed malicious actors to bypass bearer token validation routines when dispatching automated directory provisioning requests, enabling unauthorized modification of cloud user attributes and privileged IAM permission set bindings.

Technical Root Cause Analysis

Enterprise cloud environments frequently configure inbound SCIM provisioning between centralized Identity Providers (IdPs) such as Okta, Microsoft Entra ID, or PingFederate and AWS IAM Identity Center to automatically synchronize employees, groups, and role assignments.

The vulnerability stemmed from an HTTP header normalization inconsistency between AWS edge reverse proxies and the underlying Java-based SCIM provisioning microservice. When processing incoming POST /scim/v2/Groups and PATCH /scim/v2/Users requests, the microservice evaluated bearer authorization headers against cached session tokens using lenient whitespace parsing:

PATCH /scim/v2/Groups/d-9067abcdef-9901 HTTP/1.1
Host: identitycenter.us-east-1.amazonaws.com
Authorization: Bearer[tampered-token-stream]
Content-Type: application/scim+json

{
  "schemas": ["urn:ietf:params:scim:api:messages:2.0:PatchOp"],
  "Operations": [{
    "op": "add",
    "path": "members",
    "value": [{"value": "usr-attacker-id"}]
  }]
}

Because the proxy stripped trailing null bytes during transport but the internal authentication filter parsed only the initial token slice, malformed requests were processed with unauthenticated default authorization contexts. An external attacker possessing only the public SCIM endpoint URL could craft synchronization batches to insert arbitrary user identities into pre-existing groups possessing high-privilege AWS permission sets (such as AdministratorAccess or NetworkAdministrator).

Detection and Remediation Playbook

AWS confirmed that all global and sovereign cloud regions have been patched server-side with strict RFC 7644 compliant header parsers. Customer action is not required to patch the API endpoint, but security operations teams must immediately audit historical CloudTrail event streams for unauthorized identity alterations:

# CloudTrail query to inspect recent SCIM group assignment modifications
aws cloudtrail lookup-events   --lookup-attributes AttributeKey=EventName,AttributeValue=AddMemberToGroup   --start-time "2026-10-01T00:00:00Z"   --query 'Events[*].{Time:EventTime,User:Username,Detail:CloudTrailEvent}'   --output table

Security teams should also review all IAM Identity Center permission sets assigned to federated groups and enforce multi-factor authentication (MFA) step-up challenges on all high-privilege AWS account access sessions.