Vulnerability · Published Oct 20, 2026 · Assigned by GitHub_M
CVE-2026-111763A2A Java SDK send client credentials under server-controlled HTTP header name, enabling leakage via redirect
Medium 5.7
In plain English
A medium-severity security flaw in a2a-java from a2aproject. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.1% (higher than 3% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.
Official 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.
Affected packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| Maven | org.a2aproject.sdk:a2a-java-sdk-parent | 1.3.0.Final | GHSA-9rhm-2h4x-jwmx |
Affected products (as reported)
| Vendor | Product | Versions |
|---|---|---|
| a2aproject | a2a-java | < 1.3.0.Final |
Weakness: CWE-522 · 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
References
- https://github.com/a2aproject/a2a-java/security/advisories/GHSA-9rhm-2h4x-jwmx x_refsource_CONFIRM
- https://github.com/a2aproject/a2a-java/security/advisories/GHSA-4fpj-g9jf-9rgg x_refsource_MISC
- https://github.com/a2aproject/a2a-java/pull/1097 x_refsource_MISC
- https://github.com/a2aproject/a2a-java/commit/2a36530d75e11bcf9b81f543464dbe193ca6478e x_refsource_MISC
- https://github.com/a2aproject/a2a-java/releases/tag/v1.3.0.Final x_refsource_MISC