Unintended disclosure of data element to wrong session in Strands Agents SDK A2A Server

Summary

The A2A server component in Amazon Strands Agents SDK for Python before 1.43.0 and Amazon Strands Agents SDK for TypeScript before 1.5.0 does not properly isolate conversation state between callers. An authenticated remote user could read other tenants' conversation history and add persistent instructions that alter model behavior for subsequent callers via HTTP requests to the A2A endpoint using a different context_id. To mitigate this issue, users should upgrade to strands-agents 1.43.0 (Python) or @strands-agents/sdk 1.5.0 (TypeScript).

Remediation

1. Inventory every AWS strands-agents deployment, including staging.
2. Upgrade AWS strands-agents to the fixed version for your release line, listed under Affected versions.
3. Confirm the running version after the upgrade.

References

• Patchhttps://pypi.org/project/strands-agents/1.43.0/
• Patchhttps://www.npmjs.com/package/@strands-agents/sdk/v/1.5.0
• Advisoryhttps://aws.amazon.com/security/security-bulletins/2026-146-aws/
• Advisoryhttps://github.com/strands-agents/harness-sdk/security/advisories/GHSA-4v6f-7vjh-6x4m