Medium Authentication

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

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.

Published Oct 20, 2026 · Updated Oct 20, 2026 · Sources: CVE Program (cve.org) e CISA ADP, NIST National Vulnerability Database · CNA: GitHub_M

Low

Who exploits it and how urgent it is

A 0–100 score combining confirmed exploitation, ransomware and APT use, public exploits, EPSS and severity.

No exploitation signal in the sources consulted so far.

How the score was calculated

Technical severity (medium)+3

The score orders the patch queue; it does not replace your asset context (internet exposure, criticality, compensating controls).

Triage

Is it exploited, how likely is exploitation, what does it touch, and how severe do the sources call it.

Exploitation

Not confirmed

Not in CISA KEV — an absence of record, not proof it is unexploited.

EPSS FIRST

—

No EPSS score.

Affects

A2aproject

A2a-java

CVSS base

5.7

Medium · 2 source(s)

Remediation

Fixes and mitigations documented by the sources — linked to the original advisory.

No fix documented by the sources we poll. That does not mean none exists: check the vendor advisory.

First 24 hours

Ordered from the record’s own fields — exposure first, because you cannot patch what you have not found. A rule-generated starting point.

Identify exposed assets running the affected vendor/product/version combinations (A2aproject A2a-java).
No fix documented in the sources: reduce exposure and monitor the vendor advisory.
Search available logs for exploit probes matching the vulnerability class (authentication), errors and authentication anomalies.

Affected scope

Vendor, product and versions as the sources word them.

Vendor	Product	Versions	Status	Source
A2aproject	A2a-java	version < 1.3.0.Final	Vulnerable	CVE Program (cve.org) e CISA ADP

Attack characteristics

The CVSS vector, decoded. It describes the attack, not your exposure to it.

Attack vector

Local

Attack complexity

Low

Attack requirements

Present

Privileges required

Low

User interaction

None

Scope

Confidentiality (vulnerable system)

High

Integrity (vulnerable system)

None

Availability (vulnerable system)

None

Confidentiality (subsequent)

None

Integrity (subsequent)

None

Availability (subsequent)

None

Every base score collected

Sources score independently and may disagree; each row says who scored it and under which version.

Score	Version	Severity	Expl.	Impact	Scored by
5.7	CVSS 4.0	Medium	—	—	security-advisories@github.com via NIST National Vulnerability Database
5.7	CVSS 4.0	Medium	—	—	GitHub_M via CVE Program (cve.org) e CISA ADP

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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

(score shown at the top: security-advisories@github.com)

Weakness MITRE

Weakness class according to MITRE’s CWE catalog.

CWE-522 · Insufficiently Protected Credentials

Other CVEs with this weakness →

Detection

Read off the CVSS vector and the weakness class. Starting points, not tested rules.

Local/physical vector: focus on endpoint telemetry (EDR) from affected hosts.
Review authentication logs: logins without MFA, anomalous sessions and recently created accounts.

endpoint telemetry (EDR)authentication logs

Timeline

What happened to this CVE, newest first.

2026
Source status changed · Received → Awaiting Analysis
Oct 20, 2026 · NIST National Vulnerability Database
Source status changed · Published → Received
Oct 20, 2026 · NIST National Vulnerability Database
Record published
Oct 20, 2026
Affected products added · a2aproject/a2a-java
Oct 20, 2026 · CVE Program (cve.org) e CISA ADP
CVSS changed · 5.7
Oct 20, 2026 · CVE Program (cve.org) e CISA ADP
Source status changed · → Published
Oct 20, 2026 · CVE Program (cve.org) e CISA ADP
Record created in this database
Oct 20, 2026 · Alertas do Telegram
CVE published
Oct 20, 2026 · GitHub_M

Source activity

Repeated readings are counted rather than listed.

1× References added · Oct 20, 2026 – Oct 20, 2026
1× Official description updated · Oct 20, 2026 – Oct 20, 2026

References

5 on the record

github.com/a2aproject/a2a-java/releases/tag/v1.3.0.Final
x_refsource_MISC, CVE Program (cve.org) e CISA ADP
github.com/a2aproject/a2a-java/pull/1097
x_refsource_MISC, CVE Program (cve.org) e CISA ADP
github.com/a2aproject/a2a-java/security/advisories/GHSA-9rhm-2h4x-jwmx
x_refsource_CONFIRM, CVE Program (cve.org) e CISA ADP
github.com/a2aproject/a2a-java/security/advisories/GHSA-4fpj-g9jf-9rgg
x_refsource_MISC, CVE Program (cve.org) e CISA ADP
github.com/a2aproject/a2a-java/commit/2a36530d75e11bcf9b81f543464dbe193ca6478e
x_refsource_MISC, CVE Program (cve.org) e CISA ADP

Elsewhere on this site

A2aproject
every CVE for this vendor

Authentication
same class

CWE-522
other pages naming this weakness

Related CVEs (same products)

High CVE-2026-111764 A2A Java SDK has a fail-open default task authorization 14h
High CVE-2026-111765 A2A Java SDK: Android synchronous POST forwards credentials across authorities after incomplete redirect fix 14h
Medium CVE-2026-111762 A2A Java SDK: Push notification credentials logged in cleartext on protobuf parse failure 15h
Medium CVE-2026-111761 A2A Java SDK has Server-Side Request Forgery (SSRF) in push-notification delivery 15h
High CVE-2026-90819 a2aproject a2a-java Authorization Header Construction BasePushNotificationSender.java BasePushNotificationSender.dispatchNotification response splitting Sep 14, 2026
Medium CVE-2026-90820 a2aproject a2a-java AuthorizationRequestHandlerDecorator.java AuthorizationRequestHandlerDecorator.onListTasks authorization Sep 14, 2026

Not in any source we poll

Listed rather than left blank: an empty field and an unmeasured one look identical on screen, and only one is a reason to look elsewhere.

No FIRST EPSS score.
No fixed version, patch or mitigation documented.
No CISA SSVC assessment.
No confirmed IOCs, IP addresses, domains, file hashes, or malware artifacts supplied.
No organization-specific asset inventory, compensating-control status, or patch deployment evidence supplied.
No exploit packet captures, log samples, or incident case IDs supplied.

Answered from this record

Text assembled only from the fields above — no additional claims.

What should defenders know first?

CVE-2026-111763 is "A2A Java SDK send client credentials under server-controlled HTTP header name, enabling leakage via redirect", rated Medium. It affects A2a-java (A2aproject); versions are in the scope table. It is not in CISA KEV, which does not rule out exploitation. CVSS 5.7 describes technical severity. First verify whether exposed or business-critical assets run the affected versions, apply vendor fixes or mitigations, and preserve logs for review.

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