CVE-2026-15561 Red Hat CVE debrief

Who should care

Defenders responsible for systems using Red Hat JBoss Enterprise Application Platform 7.4.25 should assess exposure and prioritize verification and remediation efforts. This includes reviewing system deployments, monitoring for unusual activity, and applying provided errata from Red Hat to address the vulnerability.

Why it matters

CVE-2026-15561 is a high-severity vulnerability in EAP's undertow http/1.1 chunked-transfer decoder that allows for Denial of Service via unauthenticated connection. Defenders should prioritize verifying exposure, assessing impact, and applying remediation steps.

• Denial of Service via unauthenticated connection
• Potential for OutOfMemory errors
• Stopping of all deployments on the listener
• Need for verification of exposure and remediation

Technical summary

The vulnerability is caused by missing limits on size and count in EAP's undertow http/1.1 chunked-transfer decoder. This allows an attacker to use an unauthenticated connection to drive the JVM to an OutOfMemory error, stopping all deployments on the listener, and achieving Denial of Service. The vulnerability affects Red Hat JBoss Enterprise Application Platform 7.4.25 and potentially other versions. Defenders should prioritize verifying exposure and assessing the impact of this vulnerability on their systems, particularly those using Red Hat JBoss Enterprise Application Platform 7.4.25.

Defensive priority

Defenders should prioritize verifying exposure and assessing the impact of this vulnerability on their systems, particularly those using Red Hat JBoss Enterprise Application Platform 7.4.25.

Recommended defensive actions

• Verify if the system uses Red Hat JBoss Enterprise Application Platform 7.4.25 and assess exposure.
• Review and apply the provided errata from Red Hat to address the vulnerability.
• Monitor system deployments for unusual activity or errors related to the undertow http/1.1 chunked-transfer decoder.
• Consider implementing additional security measures to prevent similar Denial of Service attacks.
• Review compensating controls for exposed systems while remediation is scheduled and verified.
• Check relevant monitoring, detection, and logs for exposed assets that need extra review.
• Track exceptions, retest remediated assets, and close the item only after evidence is documented.

Evidence notes

The CVE record and NVD entry provide details on the vulnerability, but do not specify which versions are affected or provide remediation steps. Red Hat has provided several errata related to this vulnerability.

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.