CVE-2025-12543: Redhat Apache Camel SSRF Vulnerability

CVE-2025-12543 Overview

A critical improper input validation vulnerability has been discovered in the Undertow HTTP server core, which serves as the underlying HTTP server for WildFly, JBoss EAP, and numerous other Java-based enterprise applications. The Undertow library fails to properly validate the Host header in incoming HTTP requests, allowing requests containing malformed or malicious Host headers to be processed without rejection. This vulnerability enables attackers to poison caches, perform internal network scans, or hijack user sessions.

Critical Impact

Attackers can exploit improper Host header validation to perform cache poisoning attacks, conduct server-side request forgery (SSRF) for internal network reconnaissance, and hijack user sessions across multiple Red Hat enterprise products.

Affected Products

• Red Hat Undertow
• Red Hat JBoss Enterprise Application Platform (EAP)
• Red Hat JBoss Enterprise Application Platform Expansion Pack
• Red Hat Build of Apache Camel (Spring Boot)
• 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

Discovery Timeline

• January 7, 2026 - CVE-2025-12543 published to NVD
• March 10, 2026 - Last updated in NVD database

Technical Details for CVE-2025-12543

Vulnerability Analysis

This vulnerability stems from CWE-20 (Improper Input Validation) in the Undertow HTTP server's request handling mechanism. The core issue lies in the insufficient validation of the HTTP Host header, which is a critical component used by web applications for routing decisions, virtual host selection, and generating absolute URLs.

When the Undertow server receives an HTTP request, it processes the Host header value without proper sanitization or validation. This allows attackers to inject arbitrary values, including internal hostnames, IP addresses, or specially crafted strings designed to manipulate application behavior. The vulnerability is particularly dangerous because it can be exploited remotely without authentication, and successful exploitation can affect other users through the changed scope of the attack.

The impact extends beyond simple header manipulation—attackers can leverage this flaw to poison web caches with malicious content that gets served to legitimate users, perform reconnaissance of internal network infrastructure through server-side request forgery, and in worst-case scenarios, hijack authenticated user sessions by manipulating how the application generates URLs and cookies.

Root Cause

The root cause is improper input validation (CWE-20) in the Undertow HTTP server's Host header parsing logic. The server accepts and processes Host header values without verifying that they conform to expected formats or belong to the set of valid hostnames configured for the application. This missing validation allows attackers to supply arbitrary values that are then used in security-sensitive operations such as URL generation, routing, and cache key computation.

Attack Vector

The attack is conducted over the network by sending crafted HTTP requests to vulnerable Undertow-based applications. An attacker can manipulate the Host header to:

1. Cache Poisoning: Inject a malicious Host header that causes cached responses to be associated with attacker-controlled content
2. Internal Network Scanning: Use the Host header to trigger server-side requests to internal IP addresses and services
3. Session Hijacking: Manipulate cookie domains and redirect URLs to capture user credentials or session tokens

The attack requires user interaction (such as clicking a malicious link or visiting a compromised page) but requires no authentication, making it accessible to any network-based attacker.

The vulnerability manifests when the Undertow server parses incoming HTTP requests. An attacker sends a request with a crafted Host header containing malicious values such as internal IP addresses, localhost references, or attacker-controlled domains. The server processes these values without validation and uses them in subsequent operations. For detailed technical analysis, see the Red Hat Bug Report #2408784 and the Red Hat CVE Analysis.

Detection Methods for CVE-2025-12543

Indicators of Compromise

• HTTP access logs containing unusual Host header values such as internal IP addresses (127.0.0.1, 192.168.x.x, 10.x.x.x) or unexpected domain names
• Cache entries with mismatched Host headers compared to legitimate application domains
• Unexpected outbound connections from application servers to internal network ranges
• User session anomalies indicating potential session hijacking or cookie manipulation

Detection Strategies

• Implement web application firewall (WAF) rules to inspect and validate Host headers against a whitelist of known legitimate hostnames
• Configure network intrusion detection systems (IDS) to alert on HTTP requests containing private IP addresses or localhost in the Host header
• Enable detailed HTTP access logging and implement log analysis rules to detect anomalous Host header patterns
• Deploy application-level monitoring to track cache key generation and flag any unexpected variations

Monitoring Recommendations

• Review HTTP access logs regularly for requests with Host headers that don't match configured virtual hosts
• Monitor outbound network connections from Java application servers for unexpected internal network access patterns
• Set up alerts for cache purge operations or unusually high cache miss rates that may indicate poisoning attempts
• Track authentication and session creation events for anomalies that could indicate session hijacking

How to Mitigate CVE-2025-12543

Immediate Actions Required

• Inventory all deployments using Undertow, WildFly, JBoss EAP, or other affected Red Hat products
• Apply the appropriate security patches from Red Hat security advisories immediately
• Implement Host header validation at the web application firewall or reverse proxy level as a defense-in-depth measure
• Review application logs for any evidence of prior exploitation attempts

Patch Information

Red Hat has released security patches addressing this vulnerability across multiple product lines. Organizations should apply the relevant patches based on their deployed products:

• Red Hat Security Advisory RHSA-2026:0383
• Red Hat Security Advisory RHSA-2026:0384
• Red Hat Security Advisory RHSA-2026:0386
• Red Hat Security Advisory RHSA-2026:3889
• Red Hat Security Advisory RHSA-2026:3890
• Red Hat Security Advisory RHSA-2026:3891
• Red Hat Security Advisory RHSA-2026:3892

For detailed CVE information and patch instructions, refer to the Red Hat CVE Analysis for CVE-2025-12543.

Workarounds

• Deploy a reverse proxy (such as Apache HTTP Server or nginx) in front of Undertow-based applications and configure strict Host header validation
• Implement application-level Host header validation to reject requests with unexpected or malformed values
• Configure network segmentation to limit the impact of potential SSRF attacks originating from compromised application servers
• Disable or restrict caching mechanisms until patches can be applied to prevent cache poisoning attacks

# Example nginx configuration for Host header validation
# Add to server block to restrict allowed Host headers
if ($host !~* ^(allowed-domain\.com|www\.allowed-domain\.com)$) {
    return 444;
}