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Response snapshot Oct 26, 2026, 22:06 UTC

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VulnerabilityCVE-2026-111763

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

*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.

At a glance

Exploited
Not known
Severity
5.7 Medium (CVSS 4.0)
Chance of exploitation
0.1% in the next 30 days
Sources
1 source

What to do

GitHub lists first patched versions: org.a2aproject.sdk:a2a-java-sdk-parent: 1.3.0.Final. Confirm the affected range and upgrade guidance in the exact advisory.

Read GitHub-reviewed advisory GHSA-9rhm-2h4x-jwmx (opens a new tab)

What happened

*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 client credentials to third-party servers. Additionally, `AuthInterceptor` does not check that `location==HEADER` before placing the credential as a header.

Continue reading

**Exploit scenario.** Client configures an API key credential for agent's security scheme `myAuth`. The malicious agent returns an AgentCard where `securitySchemes` includes `myAuth` as `APIKeySecurityScheme` with `name='X-Leaked-Cred'` and `location=HEADER`. `AuthInterceptor` places the credential in the `X-Leaked-Cred` header. The agent responds with HTTP 302 redirect to `https://evil.com/collect`.

`JdkA2AHttpClient` follows the redirect, forwarding all custom headers including `X-Leaked-Cred` to `evil.com`. The attacker captures the client's credential.

**Preconditions.** - Client application has configured API key credentials via `CredentialService` for the agent's security scheme - The agent is malicious or compromised (controls its own AgentCard response) - The default `JdkA2AHttpClient` is used (with `followRedirects=NORMAL`) - The JDK version does not strip custom headers on cross-origin redirects (all current versions)

**Fix.** Validate the `APIKeySecurityScheme.name()` field against a whitelist of safe header names. Check that `apiKeySecurityScheme.location()` equals `Location.HEADER` before placing the credential as a header. Consider using `followRedirects(NEVER)` and implementing manual redirect handling that strips all authentication headers on cross-origin redirects.

**Verification.** 2/3 lens verifiers confirmed.

Affected package ranges reported by GitHub: org.a2aproject.sdk:a2a-java-sdk-parent: < 1.3.0.Final

Scores and how they were measured

CVSS base severity

5.7

Version 4.0As of

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

Measurement source (opens a new tab)

How bad it is if exploited. Not a prediction of exploitation or proof you are exposed.

EPSS probability

0.1%

Scored Percentile 3.4%

Model and measurement source (opens a new tab)

A model's estimate of exploitation in the next 30 days, not certainty or your own risk.

Related technology

Sources

  1. Primary source

    GitHub-reviewed advisory GHSA-9rhm-2h4x-jwmx (opens a new tab)

    The public advisory supplies the description, affected package/version ranges, and any listed CVSS metric. GitHub review is not local review.

    Published Checked

  2. Primary source

    GitHub public advisory API page (opens a new tab)

    The API page supplied GHSA-9rhm-2h4x-jwmx, its actual identifiers, source dates, and structured metrics.

    Published Date not suppliedChecked

  3. Primary source

    GitHub public advisory API page (opens a new tab)

    The API page supplied GHSA-9rhm-2h4x-jwmx, its actual identifiers, source dates, and structured metrics.

    Published Date not suppliedChecked

  4. Primary source

    GitHub public advisory API page (opens a new tab)

    The API page supplied GHSA-9rhm-2h4x-jwmx, its actual identifiers, source dates, and structured metrics.

    Published Date not suppliedChecked

  5. Primary source

    GitHub public advisory API page (opens a new tab)

    The API page supplied GHSA-9rhm-2h4x-jwmx, its actual identifiers, source dates, and structured metrics.

    Published Date not suppliedChecked

  6. Primary source

    GitHub public advisory API page (opens a new tab)

    The API page supplied GHSA-9rhm-2h4x-jwmx, its actual identifiers, source dates, and structured metrics.

    Published Date not suppliedChecked

  7. Primary source

    GitHub public advisory API page (opens a new tab)

    The API page supplied GHSA-9rhm-2h4x-jwmx, its actual identifiers, source dates, and structured metrics.

    Published Date not suppliedChecked

  8. Primary source

    GitHub public advisory API page (opens a new tab)

    The API page supplied GHSA-9rhm-2h4x-jwmx, its actual identifiers, source dates, and structured metrics.

    Published Date not suppliedChecked

  9. Primary source

    GitHub public advisory API page (opens a new tab)

    The API page supplied GHSA-9rhm-2h4x-jwmx, its actual identifiers, source dates, and structured metrics.

    Published Date not suppliedChecked

  10. Primary source

    GitHub public advisory API page (opens a new tab)

    The API page supplied GHSA-9rhm-2h4x-jwmx, its actual identifiers, source dates, and structured metrics.

    Published Date not suppliedChecked

  11. Primary source

    GitHub public advisory API page (opens a new tab)

    The API page supplied GHSA-9rhm-2h4x-jwmx, its actual identifiers, source dates, and structured metrics.

    Published Date not suppliedChecked

  12. Primary source

    FIRST measured EPSS score (opens a new tab)

    Measured EPSS probability and percentile for CVE-2026-111763, scored 2026-10-26. This is a model estimate, not proof of exposure.

    Published Checked

Cite this record

For factual claims, cite the primary sources above; cite KEVWire for its compilation, dates, and classifications.

APA

KEVWire. (2026, October 20). A2A Java SDK send client credentials under server-controlled HTTP header name, enabling leakage via redirect (CVE-2026-111763). https://kevwire.com/record/CVE-2026-111763

MLA

"A2A Java SDK send client credentials under server-controlled HTTP header name, enabling leakage via redirect (CVE-2026-111763)." KEVWire, 20 Oct. 2026, kevwire.com/record/CVE-2026-111763.

Chicago

KEVWire. "A2A Java SDK send client credentials under server-controlled HTTP header name, enabling leakage via redirect (CVE-2026-111763)." Last modified October 20, 2026. https://kevwire.com/record/CVE-2026-111763.

Evidence summary (plain text)

A2A Java SDK send client credentials under server-controlled HTTP header name, enabling leakage via redirect (Oct 20, 2026).
*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`
CVSS 5.7 (version 4.0; evidence as of Oct 20, 2026; https://github.com/advisories/GHSA-9rhm-2h4x-jwmx).
EPSS 0.1% for the following 30 days, scored Oct 26, 2026 (https://api.first.org/data/v1/epss?cve=CVE-2026-111763&date=2026-10-26).
Sources:
GitHub-reviewed advisory GHSA-9rhm-2h4x-jwmx: https://github.com/advisories/GHSA-9rhm-2h4x-jwmx
GitHub public advisory API page: https://api.github.com/advisories?type=reviewed&per_page=100&sort=updated&direction=desc&after=Y3Vyc29yOnYyOpK0MjAyNi0xMC0yMlQxNTo1Mjo1NlrOAAfxiA%3D%3D
GitHub public advisory API page: https://api.github.com/advisories?type=reviewed&per_page=100&sort=updated&direction=desc&after=Y3Vyc29yOnYyOpK0MjAyNi0xMC0yMlQxNDowNjoxNFrOAAfxZw%3D%3D
GitHub public advisory API page: https://api.github.com/advisories?type=reviewed&per_page=100&sort=updated&direction=desc&after=Y3Vyc29yOnYyOpK0MjAyNi0xMC0yMlQwODoyNzoyM1rOAAYp9A%3D%3D
GitHub public advisory API page: https://api.github.com/advisories?type=reviewed&per_page=100&sort=updated&direction=desc&after=Y3Vyc29yOnYyOpK0MjAyNi0xMC0yMVQyMTozNTo1OFrOAAfwCQ%3D%3D
GitHub public advisory API page: https://api.github.com/advisories?type=reviewed&per_page=100&sort=updated&direction=desc&after=Y3Vyc29yOnYyOpK0MjAyNi0xMC0yMVQyMTozMDoxM1rOAAfv2A%3D%3D
GitHub public advisory API page: https://api.github.com/advisories?type=reviewed&per_page=100&sort=updated&direction=desc&after=Y3Vyc29yOnYyOpK0MjAyNi0xMC0yMVQyMToyODowOVrOAAfv1g%3D%3D
GitHub public advisory API page: https://api.github.com/advisories?type=reviewed&per_page=100&sort=updated&direction=desc&after=Y3Vyc29yOnYyOpK0MjAyNi0xMC0yMVQyMToyNDoyMFrOAAfv1Q%3D%3D
GitHub public advisory API page: https://api.github.com/advisories?type=reviewed&per_page=100&sort=updated&direction=desc&after=Y3Vyc29yOnYyOpK0MjAyNi0xMC0yMVQyMDo0NTowN1rOAAfvzQ%3D%3D
GitHub public advisory API page: https://api.github.com/advisories?type=reviewed&per_page=100&sort=updated&direction=desc&after=Y3Vyc29yOnYyOpK0MjAyNi0xMC0yMVQyMDozMDoyNlrOAAfvxw%3D%3D
GitHub public advisory API page: https://api.github.com/advisories?type=reviewed&per_page=100&sort=updated&direction=desc&after=Y3Vyc29yOnYyOpK0MjAyNi0xMC0yMVQyMDowMzo1N1rOAAfvxQ%3D%3D
FIRST measured EPSS score: https://api.first.org/data/v1/epss?cve=CVE-2026-111763&date=2026-10-26
Record ID: CVE-2026-111763.
Record origin: Ingested record.
AI evidence: Not assessed.
Known exploitation: Not assessed.
Zero-day status: Not assessed. KEV membership alone does not establish zero-day status.
About this data

This record was ingested from a data source. Retrieved: Oct 26, 2026, 19:40 UTC. Ingestion is not an independent editorial investigation.

A CISA KEV listing documents known exploitation, not necessarily a zero-day; absence from the catalog does not prove a vulnerability has never been exploited.

Technology tags indicate possible relevance, not verified exposure. Confirm the affected product, version, and configuration against your own inventory; KEVWire does not scan your systems.

A personal reading checklist on this device, not verified remediation.

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