Undertow HTTP Server Fails to Reject Malformed Host Headers Leading to Potential Cache Poisoning and SSRF
Summary
Undertow HTTP Server Fails to Reject Malformed Host Headers Leading to Potential Cache Poisoning and SSRF. Red Hat rates this important (CVSS 9.6). Weakness: CWE-20. Affected package(s): eap8-wildfly, eap8-undertow, eap8-apache-cxf, eap8-wildfly-clustering, eap8-bouncycastle, eap7-undertow. Resolved in Red Hat advisory RHSA-2026:3889 — update the affected packages (`sudo dnf update`).
- eap8-wildfly-0:8.1.3-4.GA_redhat_00006.1.el8eap
- eap8-undertow-0:2.3.20-2.SP4_redhat_00001.1.el9eap
- eap8-apache-cxf-0:4.0.10-1.redhat_00001.1.el8eap
- eap8-wildfly-clustering-0:5.0.12-1.Final_redhat_00001.1.el9eap
- eap8-bouncycastle-0:1.82.0-1.redhat_00001.1.el9eap
- eap7-undertow-0:1.4.18-21.SP19_redhat_00001.1.ep7.el7
- eap8-jaxb-0:4.0.6-1.redhat_00001.1.el8eap
- eap8-wildfly-elytron-0:2.6.6-1.Final_redhat_00001.1.el8eap
- eap8-undertow-0:2.3.23-1.SP3_redhat_00001.1.el8eap
- eap8-jboss-el-api_5.0_spec-0:4.0.2-1.Final_redhat_00001.1.el8eap
- eap8-wildfly-javadocs-0:8.1.1-4.GA_redhat_00007.1.el8eap
- io.undertow/undertow-core:2.2.39.Final-redhat-00001
Official advisory · high-confidence parse· fetched 5 hours ago·verify at source
- RHSA-2026:3889
Official advisory · high-confidence parse· fetched 5 hours ago·verify at source
Mitigation checklist
- Update the affected package(s) to the fixed version shipped in RHSA-2026:3889 (`sudo dnf update` / `yum update`).
Official advisory · high-confidence parse· fetched 5 hours ago·verify at source
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