A2A Java SDK send client credentials under server-controlled HTTP header name, enabling leakage via redirect

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS 4.0

5.7 · 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 · score source

EPSS

• CVE-2026-111763: 0.14% estimated exploitation activity in the next 30 days; percentile 3.43 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Impact. A malicious or compromised A2A agent can cause the client's API key credential to be forwarded to an arbitrary third-party server. The agent serves an AgentCard with an APIKeySecurityScheme specifying a custom header name, then responds with an HTTP redirect. The JDK HttpClient follows the redirect and forwards the custom header containing the credential, since only the standard Authorization header may be stripped on cross-origin redirects. Where. client/transport/spi/src/main/java/org/a2aproject/sdk/client/transport/spi/interceptors/auth/AuthInterceptor.java:69 in intercept What. The apiKeySecurityScheme.name() field from the remote agent's AgentCard (untrusted, server-controlled data) is used directly as the HTTP header name when placing client credentials. Combined with JdkA2AHttpClient's followRedirects(NORMAL) policy, credentials under custom header names survive cross-origin redirects (only Authorization is stripped on newer JDKs), allowing a malicious agent to leak…

Published by the source

20 Oct 2026, 21:04 UTC

Last modified by the source

21 Oct 2026, 03:11 UTC

Source last checked

26 Oct 2026, 16:58 UTC

1. Revision 3 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-9rhm-2h4x-jwmx

2. Revision 2 · amended · 25 Oct 2026

   Reviewed OSV alias/range/CVSS4 correction; package source scopes and original publication preserved. No customer finding resolved.

3. Revision 1 · created · 24 Oct 2026

   Published from osv record GHSA-9rhm-2h4x-jwmx

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# Patch Next advisory brief: CVE-2026-111763

Advisory: A2A Java SDK send client credentials under server-controlled HTTP header name, enabling leakage via redirect
IDs: CVE-2026-111763, GHSA-9rhm-2h4x-jwmx
Record: https://patchnext.com/advisories/cve-2026-111763 (revision 3, source checked 26 Oct 2026, 16:58 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Medium (CVSS 5.7)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: org.a2aproject.sdk:a2a-java-sdk-parent 1.3.0.Final. A vendor fix does not mean a deployment is fixed.

## Affected components
- Maven org.a2aproject.sdk:a2a-java-sdk-parent: affected < 1.3.0.Final; fixed in 1.3.0.Final

## Suggested inspection (read-only)
- Maven org.a2aproject.sdk:a2a-java-sdk-parent: check the installed version with your package manager.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on org.a2aproject.sdk:a2a-java-sdk-parent.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://osv.dev/vulnerability/GHSA-9rhm-2h4x-jwmx (OSV record GHSA-9rhm-2h4x-jwmx lists affected ranges: Maven org.a2aproject.sdk:a2a-java-sdk-parent >=0 <1.3.0.Final (fixed))
- Verified: https://github.com/advisories/GHSA-9rhm-2h4x-jwmx (GitHub-reviewed advisory GHSA-9rhm-2h4x-jwmx lists affected ranges: Maven org.a2aproject.sdk:a2a-java-sdk-parent >=0 <1.3.0.Final)

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