A2A Java SDK: Android synchronous POST forwards credentials across authorities after incomplete redirect fix

Why it is Amber

• CVSS 7.5 high
• Remotely exploitable without logging in
• On your watchlist: Maven

Affected packages

References

• https://github.com/advisories/GHSA-4fpj-g9jf-9rgg
• https://github.com/a2aproject/a2a-java/security/advisories/GHSA-4fpj-g9jf-9rgg
• https://github.com/a2aproject/a2a-java/security/advisories/GHSA-9rhm-2h4x-jwmx
• https://nvd.nist.gov/vuln/detail/CVE-2026-111765
• https://github.com/a2aproject/a2a-java/pull/1141
• https://github.com/a2aproject/a2a-java/commit/2a36530d75e11bcf9b81f543464dbe193ca6478e
• https://github.com/a2aproject/a2a-java/commit/3ae82912a106a6765d7b78042b0ef96e6c2e29b5
• https://github.com/a2aproject/a2a-java/blob/30e31086e24bea096b5f662088661269c9119100/SECURITY.md#L335-L342
• https://github.com/a2aproject/a2a-java/releases/tag/v1.3.2.Final
• https://github.com/advisories/GHSA-4fpj-g9jf-9rgg

Original description

A2A Java SDK is the official Java SDK for the Agent2Agent (A2A) Protocol. Starting in version 1.3.0.Final and prior to version 1.3.2.Final, the AndroidA2AHttpClient synchronous POST path overrides the disabled-redirect setting in AndroidA2AHttpClient.createConnection() with the PostBuilder default followRedirects value of true, leaving a residual of the earlier credential-redirect fix. JSONRPCTransport and RestTransport add interceptor-produced authentication headers and call synchronous post() without disabling redirects. AuthInterceptor permits X-API-Key, API-Key, X-Auth-Token, and X-Authentication headers; Android's repackaged OkHttp strips Authorization on cross-authority redirects but retains these nonstandard headers, disclosing a complete configured API key or token to another authority. The additional exposure applies when redirect or front-door behavior is compromised separately from the credential-handling component, or those components operate in different trust domains; a completely malicious initial origin already receives the credential on the first request. Autonomous clients require no human action, while user-invoked workflows can require interaction. Explicit followRedirects(false) prevents the redirected request. The demonstrated impact is credential disclosure, not subsequent credential use, integrity or availability impact, code execution, or host compromise. This issue is fixed in version 1.3.2.Final.