CVE-2026-28369 Red Hat CVE debrief

Who should care

Defenders responsible for Undertow-based systems, especially those with publicly accessible web interfaces, should assess their exposure and take necessary actions to mitigate the vulnerability.

Why it matters

CVE-2026-28369 allows remote attackers to perform request smuggling in Undertow, potentially bypassing security mechanisms or accessing restricted information. Defenders should verify exposure, especially for publicly accessible Undertow-based systems, and apply vendor-provided patches or mitigations.

• Potential bypass of security mechanisms
• Possible access to restricted information
• Potential manipulation of web caches
• Verification of exposure and patching/mitigation priority

Technical summary

The vulnerability in Undertow allows remote attackers to perform request smuggling by exploiting incorrect processing of HTTP requests with leading spaces in the first header line. This behavior, which violates HTTP standards, could potentially allow attackers to bypass security mechanisms, access restricted information, or manipulate web caches. The vulnerability is caused by the incorrect stripping of leading spaces in the first header line of HTTP requests. Attackers can exploit this vulnerability to send multiple requests through a single connection, potentially leading to unauthorized actions or data exposure. Defenders should prioritize verifying exposure of Undertow-based systems, especially those with

Defensive priority

Defenders should prioritize verifying exposure of Undertow-based systems, especially those with publicly accessible web interfaces, and apply vendor-provided patches or mitigations.

Recommended defensive actions

• Verify exposure of Undertow-based systems, especially those with publicly accessible web interfaces
• Apply vendor-provided patches or mitigations
• Monitor for suspicious traffic patterns that could indicate request smuggling attempts
• Review and update security configurations for Undertow-based applications
• Perform a thorough review of system logs to identify potential request smuggling attempts
• Implement additional security measures such as web application firewalls
• Conduct regular security audits to ensure compliance with security best practices

Evidence notes

The CVE record and NVD entry provide details on the vulnerability in Undertow, including its potential impact and affected products. However, specific version information and exploitation details are not provided, requiring further verification.

Sources and references

Methodology and review provenance

AI-assisted synthesis based on stored public vulnerability evidence. System validation, approval state, and publication status do not by themselves establish human review of this revision. PatchSiren helps prioritize defensive review and does not prove exposure or remediation on any system.