CVE-2026-9561: Eclipse Kura Auth Bypass Vulnerability

CVE-2026-9561 Overview

CVE-2026-9561 affects Eclipse Kura versions prior to 5.6.2. The vulnerability stems from insufficient validation of the client-supplied X-Forwarded-For HTTP header, which Kura treats as the authoritative source of the client IP address in audit log entries. The org.eclipse.kura.web2 Web Console and org.eclipse.kura.rest.provider REST API components rely on this header when initializing audit context. The org.eclipse.kura.jetty.customizer unconditionally installs Jetty's ForwardedRequestCustomizer on all HTTP and HTTPS connectors. This causes HttpServletRequest.getRemoteAddr() to return the attacker-controlled header value, enabling IP spoofing in logs and downstream security controls [CWE-345].

Critical Impact
Unauthenticated remote attackers can bypass IP-based brute-force protections such as fail2ban or trigger denial of service by causing a victim's IP address to be banned.

Affected Products

Eclipse Kura versions prior to 5.6.2
org.eclipse.kura.web2 Web Console component
org.eclipse.kura.rest.provider REST API component

Discovery Timeline

2026-07-14 - CVE-2026-9561 published to NVD
2026-07-14 - Last updated in NVD database

Technical Details for CVE-2026-9561

Vulnerability Analysis

Eclipse Kura is an open-source IoT edge framework that provides web and REST management interfaces. The framework registers Jetty's ForwardedRequestCustomizer on every HTTP and HTTPS connector without conditional gating. This customizer parses the X-Forwarded-For header and rewrites the value returned by HttpServletRequest.getRemoteAddr().

Downstream audit logic in the Web Console and REST provider treats this rewritten value as the authoritative source IP. Any external client can inject an arbitrary IP address into audit records by adding a single HTTP header. The vulnerability applies regardless of whether Kura sits behind a trusted reverse proxy.

Root Cause

The root cause is unconditional trust in a client-supplied header, categorized as Insufficient Verification of Data Authenticity [CWE-345]. Jetty's ForwardedRequestCustomizer is designed for deployments behind trusted proxies that overwrite forwarded headers. Kura installs the customizer globally without validating whether the request originated from a trusted upstream. Audit code paths then use getRemoteAddr() as the primary IP source instead of the actual TCP peer address.

Attack Vector

An unauthenticated remote attacker sends HTTP requests to the Kura Web Console or REST API with a forged X-Forwarded-For header. Two attack scenarios apply. First, an attacker conducting brute-force authentication attempts can rotate spoofed IP values on each request, evading fail2ban and similar controls that parse Kura audit logs for repeat offenders. Second, an attacker can inject a victim's IP address to poison log-driven blocklists, causing legitimate traffic from that address to be banned. Because the header is trusted before authentication, no credentials or user interaction are required.

Refer to the Eclipse CVE Assignment Work Item for additional technical details.

Detection Methods for CVE-2026-9561

Indicators of Compromise

Audit log entries showing X-Forwarded-For values that do not correspond to expected upstream proxies or network topology.
Repeated authentication failures in Kura audit logs originating from rapidly rotating or non-routable IP addresses.
Log entries attributing activity to internal, loopback, or reserved address ranges when Kura is exposed on public networks.

Detection Strategies

Correlate Kura application audit logs against network-layer flow data or reverse proxy access logs to identify divergence between reported and actual client IPs.
Alert on inbound HTTP requests to Kura endpoints containing X-Forwarded-For headers when no legitimate upstream proxy is deployed.
Monitor authentication failure patterns that show identical user agents or request timings across many distinct claimed source IPs.

Monitoring Recommendations

Ingest Kura Web Console and REST API logs into a centralized SIEM with the original TCP peer address preserved from load balancer or firewall telemetry.
Track failed login volume per real source IP rather than per header-derived IP to restore effective brute-force detection.
Baseline expected X-Forwarded-For values from trusted proxies and flag deviations for investigation.

How to Mitigate CVE-2026-9561

Immediate Actions Required

Upgrade Eclipse Kura to version 5.6.2 or later, where header handling is corrected.
Restrict network exposure of the Kura Web Console and REST API to trusted management networks until patching completes.
Reconfigure fail2ban and equivalent tools to consume IP data from network-layer sources rather than Kura audit logs.

Patch Information

Eclipse Kura 5.6.2 addresses the vulnerability. Review the Eclipse CVE Assignment Work Item for patch details and version guidance before deploying updates.

Workarounds

Place Kura behind a reverse proxy that strips or overwrites the X-Forwarded-For header from untrusted clients before forwarding requests.
Configure network access controls to permit connections to Kura HTTP and HTTPS connectors only from trusted proxy addresses.
Temporarily disable log-driven IP banning integrations that rely on Kura-reported client IPs until the upgrade is applied.

bash

# Example nginx directive to sanitize forwarded headers before proxying to Kura
proxy_set_header X-Forwarded-For $remote_addr;
proxy_set_header X-Real-IP $remote_addr;