RHSA-2026:55800: Important: haproxy security update
The haproxy packages provide a reliable, high-performance network load balancer for TCP and HTTP-based applications.Security Fix(es): haproxy: HAProxy: Denial of Service via HPACK dynamic table insertions (CVE-2026-55204) haproxy: HAProxy: Response smuggling due to integer overflow in FastCGI record length handling (CVE-2026-55203) For more details about the security issue(s), including the impact, a CVSS score, acknowledgments, and other related information, refer to the CVE page(s) listed in the References section.
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Upgrade
Upgrade
redhat/haproxyto a version that resolves this vulnerability.Fixed in 3.0.5-4.el10_0.3 - Upgrade
Upgrade
redhat/haproxy-debuginfoto a version that resolves this vulnerability.Fixed in 3.0.5-4.el10_0.3 - Upgrade
Upgrade
redhat/haproxy-debugsourceto a version that resolves this vulnerability.Fixed in 3.0.5-4.el10_0.3 - Upgrade
Upgrade
redhat/haproxyto a version that resolves this vulnerability.Fixed in 3.0.5-4.el10_0.3.aa - Upgrade
Upgrade
redhat/haproxy-debuginfoto a version that resolves this vulnerability.Fixed in 3.0.5-4.el10_0.3.aa - Upgrade
Upgrade
redhat/haproxy-debugsourceto a version that resolves this vulnerability.Fixed in 3.0.5-4.el10_0.3.aa - Upgrade
Upgrade
haproxyto a version that resolves this vulnerability.Patch CVE-2026-55203 - Upgrade
Upgrade
haproxyto a version that resolves this vulnerability.Patch CVE-2026-55204
Event History
Frequently Asked Questions
Which deployed software should be checked?
Systems using the Red Hat haproxy packages are in scope, including the associated haproxy-debuginfo and haproxy-debugsource packages listed in the advisory.
What attack paths are addressed by this update?
The update addresses two distinct issues: denial of service through HPACK dynamic-table insertions and response smuggling caused by integer overflow when handling FastCGI record lengths. Exposure therefore depends on use of the affected HAProxy functionality, but the advisory does not provide configuration-specific conditions or mitigations.
How can I track whether the relevant fixes have been applied?
The advisory identifies the fixes as CVE-2026-55204 and CVE-2026-55203. Check installed HAProxy packages against the Red Hat advisory and its referenced Bugzilla records to determine update status.