CVE-2026-28369: Apache Camel Hawtio Auth Bypass Flaw

CVE-2026-28369 Overview

A critical HTTP Request Smuggling vulnerability has been discovered in Red Hat Undertow, the high-performance Java web server used by JBoss and numerous enterprise applications. When Undertow receives an HTTP request where the first header line starts with one or more spaces, it incorrectly processes the request by stripping these leading spaces. This behavior violates HTTP standards and can be exploited by remote attackers to perform request smuggling attacks.

Request smuggling allows attackers to bypass security mechanisms, access restricted information, or manipulate web caches, potentially leading to unauthorized actions or sensitive data exposure. The vulnerability affects a wide range of Red Hat enterprise products that utilize Undertow as their underlying web server component.

Critical Impact

Remote attackers can exploit this HTTP parsing flaw to bypass security controls, access restricted resources, and manipulate web application behavior without authentication.

Affected Products

• Red Hat Undertow
• Red Hat JBoss Enterprise Application Platform 7.0.0 and 8.0.0
• Red Hat Build of Apache Camel - Hawtio 4.0
• Red Hat Build of Apache Camel for Spring Boot 4.0
• Red Hat Data Grid 8.0
• Red Hat Fuse 7.0.0
• Red Hat Process Automation 7.0
• Red Hat Single Sign-On 7.0
• Red Hat JBoss Enterprise Application Platform Expansion Pack
• Red Hat Enterprise Linux 9.0

Discovery Timeline

• 2026-03-27 - CVE-2026-28369 published to NVD
• 2026-03-31 - Last updated in NVD database

Technical Details for CVE-2026-28369

Vulnerability Analysis

This vulnerability (CWE-444: Inconsistent Interpretation of HTTP Requests) stems from Undertow's non-compliant handling of HTTP request headers. When processing incoming HTTP requests, Undertow strips leading whitespace characters from the first header line rather than rejecting the malformed request as required by HTTP specifications.

This parsing inconsistency creates a desynchronization between Undertow and upstream or downstream HTTP components (proxies, load balancers, or other web servers). When these components interpret the same HTTP traffic differently, attackers can craft specially formatted requests that appear as one request to frontend security devices but are interpreted as multiple requests by the backend Undertow server.

The impact is significant: successful exploitation enables bypass of access controls, web cache poisoning, credential hijacking, and unauthorized access to sensitive application functionality. The network attack vector with no required privileges or user interaction makes this vulnerability particularly dangerous in internet-facing deployments.

Root Cause

The root cause lies in Undertow's HTTP parser implementation, which fails to properly validate the start of HTTP header lines according to RFC specifications. Instead of rejecting requests with leading whitespace characters in the header line (which indicate either obsolete line folding or malformed input), Undertow silently strips these characters and continues processing.

This permissive parsing behavior creates an opportunity for HTTP desynchronization attacks. RFC 7230 explicitly deprecates line folding in headers and recommends that recipients reject messages containing such syntax when it appears in critical positions.

Attack Vector

The attack exploits the discrepancy between how Undertow and intermediary HTTP components (such as reverse proxies or load balancers) parse HTTP requests. An attacker sends a crafted HTTP request with leading spaces in the header line, which may be interpreted differently by each component in the request chain.

For example, a frontend proxy might see a single request while Undertow interprets the smuggled content as a second, separate request. This allows the attacker to inject unauthorized requests that bypass frontend security controls, potentially accessing protected endpoints, hijacking other users' sessions, or poisoning cache entries.

The attack requires network access to the vulnerable Undertow instance and can be executed without authentication, making it exploitable by any remote attacker who can send HTTP traffic to the target system.

Detection Methods for CVE-2026-28369

Indicators of Compromise

• HTTP access logs showing unusual request patterns with malformed or unexpected header formatting
• Application logs indicating request parsing anomalies or header validation errors
• Evidence of unauthorized access to protected resources without corresponding authentication events
• Web cache entries containing unexpected or malicious content
• Discrepancies between proxy/load balancer logs and backend Undertow server logs for the same traffic

Detection Strategies

• Deploy network intrusion detection rules to identify HTTP requests with leading whitespace in header lines
• Implement log correlation between frontend proxies and backend Undertow servers to detect request count discrepancies
• Monitor for unusual patterns of requests appearing to originate from internal or trusted sources
• Review web application firewall (WAF) logs for blocked or suspicious HTTP requests targeting parsing inconsistencies

Monitoring Recommendations

• Enable detailed HTTP access logging on both reverse proxies and Undertow servers
• Configure alerting for HTTP parsing errors or malformed request rejections
• Implement real-time monitoring of authentication bypass attempts and unauthorized resource access
• Deploy application-layer traffic analysis to detect HTTP desynchronization patterns

How to Mitigate CVE-2026-28369

Immediate Actions Required

• Review the Red Hat CVE-2026-28369 Advisory for the latest patch availability
• Identify all Undertow deployments in your environment, including embedded instances in JBoss EAP and other Red Hat products
• Prioritize patching internet-facing and high-value target systems
• Consider implementing temporary mitigations such as WAF rules while awaiting patches

Patch Information

Red Hat has acknowledged this vulnerability and is tracking it through Bug Report #2443262. Organizations should monitor the Red Hat Customer Portal and security advisories for official patch releases for affected products including:

• Undertow (core library)
• JBoss Enterprise Application Platform 7.x and 8.x
• Build of Apache Camel - Hawtio 4.0
• Build of Apache Camel for Spring Boot 4.0
• Data Grid 8.0
• Fuse 7.0.0
• Process Automation 7.0
• Single Sign-On 7.0

Apply vendor-provided security updates as soon as they become available.

Workarounds

• Configure frontend reverse proxies or load balancers to normalize HTTP requests and reject those with leading whitespace in headers
• Deploy a Web Application Firewall (WAF) with rules to block malformed HTTP requests
• Implement strict HTTP parsing on edge devices to filter non-compliant requests before they reach Undertow
• Consider adding an additional HTTP normalization layer between external traffic and Undertow servers
• Limit network exposure of vulnerable Undertow instances until patches are applied

# Example: Configure HAProxy to reject requests with malformed headers
# Add to frontend configuration to normalize HTTP traffic

frontend http_in
    bind *:80
    # Reject requests with whitespace at start of header lines
    http-request deny if { req.hdr_cnt(X-) -m reg ^[[:space:]] }
    # Enable strict HTTP mode to reject non-compliant requests
    option httplog
    option http-server-close
    default_backend undertow_servers