CVE-2026-85511 Overview
CVE-2026-85511 is a flaw in Red Hat JBoss Enterprise Application Platform (EAP) affecting the Elytron security subsystem. The vulnerability exists in applications whose security domain is backed by an Elytron token-realm configured with oauth2-introspection. Missing URL encoding of user-supplied values permits parameter substitution when the introspection request is constructed. The weakness is categorized under [CWE-290: Authentication Bypass by Spoofing]. Red Hat has issued advisories RHSA-2026:70228, RHSA-2026:70229, RHSA-2026:70230, and RHSA-2026:70277 to address impacted EAP releases.
Critical Impact
An authenticated attacker can manipulate OAuth2 introspection request parameters, potentially influencing token validation outcomes and impacting confidentiality and integrity of the authentication flow.
Affected Products
- Red Hat JBoss Enterprise Application Platform (EAP) with Elytron token-realm
- EAP security domains using OAuth2 introspection endpoints
- Downstream Red Hat products referenced in advisories RHSA-2026:70228, RHSA-2026:70229, RHSA-2026:70230, and RHSA-2026:70277
Discovery Timeline
- 2026-09-18 - CVE-2026-85511 published to NVD
- 2026-09-22 - Last updated in NVD database
Technical Details for CVE-2026-85511
Vulnerability Analysis
The flaw resides in the Elytron token-realm implementation that integrates with OAuth2 introspection endpoints. When EAP validates a bearer token, it issues an introspection request to the configured authorization server. Elytron constructs the request body using values derived from client-supplied input without applying URL encoding. An attacker who can influence those values can inject additional parameters into the application/x-www-form-urlencoded payload. This parameter substitution alters the introspection request and can affect how the authorization server interprets the query. The result is a spoofing weakness in the token validation path aligned with [CWE-290].
Root Cause
The root cause is missing URL encoding of untrusted input incorporated into the OAuth2 introspection request. Special characters such as & and = pass unescaped into the form-encoded body, allowing additional key/value pairs to be smuggled alongside the intended token parameter.
Attack Vector
Exploitation requires network access to the EAP application and low-privilege authentication context. The high attack complexity reflects reliance on specific token-realm configurations and the ability to shape a token value or related field that reaches the introspection client. Successful exploitation impacts token validation semantics rather than yielding direct code execution.
No verified public proof-of-concept code is available. See the Red Hat CVE-2026-85511 advisory and Red Hat Bug Report #2483140 for further technical details.
Detect Identity Attacks the Moment Authentication Fails
Singularity™ Identity surfaces credential misuse, lateral movement, and privilege escalation in real time, so you can contain the breach before it spreads.
Stop Identity AttacksDetection Methods for CVE-2026-85511
Indicators of Compromise
- Unexpected additional parameters appearing in OAuth2 introspection request bodies logged by the authorization server.
- Introspection requests containing unescaped & or = characters within the token field value.
- Anomalous authentication successes for tokens that should have been rejected by the identity provider.
Detection Strategies
- Enable verbose logging on the OAuth2 introspection endpoint and inspect raw request bodies for parameter injection patterns.
- Correlate EAP Elytron authentication events with authorization-server introspection responses to identify mismatched decisions.
- Deploy web application firewall rules that flag reserved URL characters embedded within bearer token values presented to EAP.
Monitoring Recommendations
- Monitor Elytron audit logs for authentication events tied to token-realm security domains.
- Alert on repeated introspection failures followed by successful authentications from the same client.
- Track configuration drift on EAP security domains to detect unauthorized oauth2-introspection changes.
How to Mitigate CVE-2026-85511
Immediate Actions Required
- Inventory all EAP deployments using Elytron token-realm with oauth2-introspection and prioritize them for patching.
- Apply the fixed packages delivered in RHSA-2026:70228, RHSA-2026:70229, RHSA-2026:70230, or RHSA-2026:70277 matching your EAP release.
- Rotate any bearer tokens or client credentials that may have transited a vulnerable introspection flow.
Patch Information
Red Hat has released patches through the following advisories: RHSA-2026:70228, RHSA-2026:70229, RHSA-2026:70230, and RHSA-2026:70277. Administrators should consult the Red Hat CVE-2026-85511 advisory to map affected components to the correct erratum.
Workarounds
- Where patching is not immediately possible, restrict access to EAP applications relying on oauth2-introspection to trusted network segments.
- Enforce strict input validation on any client-facing field that can propagate into the token introspection request.
- Consider temporarily switching the security domain to a non-OAuth2 realm until the patched EAP release is deployed.
# Configuration example
# See Red Hat advisories for exact remediation steps for your EAP version
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
