Undertow — CraftedSignal Threat Feed

Red Hat Undertow Multiple Vulnerabilities Allow Security Bypass

hello@craftedsignal.io — Mon, 30 Mar 2026 11:24:09 +0000

Red Hat Undertow is vulnerable to multiple security flaws that could allow an unauthenticated, remote attacker to bypass security restrictions, manipulate data, and expose sensitive information. The specifics of these vulnerabilities are not detailed, but the advisory indicates a high severity due to the potential impact. Without further information, defenders should assume all versions of Undertow are affected. This lack of specific CVEs or exploitation details makes precise mitigation challenging. Defenders should focus on broad detection strategies for anomalous activity related to Undertow deployments.

Attack Chain

The attacker identifies a vulnerable Red Hat Undertow instance exposed to the internet.
The attacker sends a specially crafted HTTP request designed to exploit one of the undisclosed vulnerabilities.
The vulnerable Undertow instance processes the malicious request, leading to a security bypass.
The attacker exploits the bypassed security measure to manipulate data within the application.
The attacker leverages another vulnerability to gain unauthorized access to sensitive information stored within the application or backend systems.
The attacker exfiltrates the compromised data or uses it to further compromise the system.
The attacker maintains persistence by creating backdoors.

Impact

Successful exploitation of these vulnerabilities could lead to significant data breaches, unauthorized modification of critical application data, and complete compromise of the affected system. The lack of specific vulnerability details makes it difficult to quantify the exact number of potential victims or targeted sectors. The impact ranges from data theft and service disruption to complete system takeover, depending on the specific vulnerabilities exploited and the application’s role.

Recommendation

Monitor web server logs (category: webserver, product: linux) for suspicious HTTP requests, particularly those with unusual URI patterns or excessive length, using the provided Sigma rule.
Implement rate limiting and input validation on all Undertow deployments to mitigate potential exploitation attempts.
Review access control configurations for all applications using Undertow to ensure least privilege principles are enforced.

Undertow Request Smuggling Vulnerability (CVE-2026-28368)

hello@craftedsignal.io — Sat, 28 Mar 2026 12:00:00 +0000

CVE-2026-28368 is a critical vulnerability found in the Undertow web server. This flaw enables a remote attacker to craft specialized HTTP requests that Undertow parses differently compared to upstream proxies. This discrepancy allows attackers to conduct request smuggling attacks, effectively bypassing security measures and potentially gaining unauthorized access to sensitive resources. The vulnerability stems from inconsistent interpretation of HTTP requests, which is a common issue in web…

Undertow HTTP Request Smuggling Vulnerability (CVE-2026-28367)

hello@craftedsignal.io — Fri, 27 Mar 2026 17:16:27 +0000

CVE-2026-28367 is a request smuggling vulnerability found in Undertow, a flexible performant server-side Java web server. The vulnerability arises from improper handling of HTTP header block terminators. Specifically, a remote attacker can send \r\r\r as a header block terminator, which can be misinterpreted by certain proxy servers. This allows the attacker to potentially smuggle malicious requests, bypassing security controls and gaining unauthorized access to resources or manipulating…

Red Hat JBoss Enterprise Application Platform Multiple Vulnerabilities

hello@craftedsignal.io — Wed, 25 Mar 2026 10:23:05 +0000

Multiple vulnerabilities exist within the Red Hat JBoss Enterprise Application Platform. An unauthenticated, remote attacker can exploit these flaws to trigger a denial-of-service (DoS) condition, manipulate sensitive data, and facilitate subsequent attacks, including cache poisoning and session hijacking. The vulnerabilities exist in the Undertow component. While specific CVEs are not listed in the advisory, the impact could be significant, leading to service disruption and potential data compromise. Defenders should focus on patching and monitoring for suspicious activity targeting JBoss instances.

Attack Chain

The attacker identifies a vulnerable JBoss Enterprise Application Platform instance running an outdated version of Undertow.
The attacker sends a specially crafted HTTP request designed to exploit a specific vulnerability within Undertow’s request processing logic.
If the vulnerability leads to a DoS, the server’s resources are exhausted, causing it to become unresponsive to legitimate requests.
If the vulnerability allows data manipulation, the attacker modifies application data via HTTP requests.
For cache poisoning, the attacker crafts a request that, when cached by the application or a proxy, serves malicious content to other users.
For session hijacking, the attacker exploits a vulnerability that allows them to steal or forge user session IDs.
The attacker uses the hijacked session to impersonate a legitimate user and gain unauthorized access to sensitive resources.

Impact

Successful exploitation of these vulnerabilities can lead to significant disruption of services relying on the JBoss Enterprise Application Platform. This includes denial-of-service conditions, potentially impacting business operations and user experience. Data manipulation could lead to data corruption or unauthorized modification of sensitive information. Cache poisoning can spread malicious content to a wide range of users. Session hijacking allows attackers to gain unauthorized access, potentially leading to data breaches or further malicious activity.

Recommendation

Examine web server logs for abnormal HTTP requests that could indicate exploitation attempts (see example Sigma rule for detecting suspicious HTTP methods).
Monitor network traffic for unusual patterns that may indicate denial-of-service attacks targeting JBoss servers.
Implement a Web Application Firewall (WAF) to filter out malicious requests and protect against common web exploits.
Apply the latest patches and updates for Red Hat JBoss Enterprise Application Platform, focusing on the Undertow component, to remediate the underlying vulnerabilities.