CVE-2026-109575 HAProxy CVE debrief

Who should care

HAProxy Data Plane API users, administrators, and security teams should assess exposure and prioritize remediation. This vulnerability has significant implications for HAProxy Data Plane API users, as it could allow unauthorized access to sensitive configuration data and complete control of the API. Users should review their current version and upgrade to a fixed version as soon as possible.

Why it matters

CVE-2026-109575 is a critical vulnerability in HAProxy Data Plane API that allows unauthenticated attackers to bypass credentials and gain full API administrative access, potentially leading to unauthorized access to sensitive configuration data and complete control of the API.

• Unauthenticated attackers can bypass credentials to gain full API administrative access
• Sensitive, cleartext HAProxy configuration data can be read or replaced
• Unauthorized remote or local actors can access the managed configuration entirely via the raw configuration endpoint

Technical summary

The vulnerability is caused by process-global authentication logic that improperly drops security controls across multiple transport types. When a TLS Certificate Authority (tls_ca) is configured and a numeric TLS port (tls_port) is specified, the application globally disables Basic authentication on its shared internal request handler. This allows an attacker to bypass authentication and gain full API administrative access. The vulnerability affects HAProxy Data Plane API versions 2.2.0 through 3.4.3 and has been fixed in versions 3.4.4, 3.3.9, 3.2.17, 3.0.25, and 2.9.29.

Defensive priority

High

Recommended defensive actions

• Upgrade to a fixed version of HAProxy Data Plane API (3.4.4, 3.3.9, 3.2.17, 3.0.25, or 2.9.29)
• Implement mutual TLS (mTLS) client certificate verification for all non-mTLS listeners
• Restrict access to the HAProxy Data Plane API to only trusted users and networks
• 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
• Confirm whether affected product deployments exist in managed environments and assign an owner for follow-up

Evidence notes

The vulnerability is caused by process-global authentication logic that improperly drops security controls across multiple transport types. When a TLS Certificate Authority (tls_ca) is configured and a numeric TLS port (tls_port) is specified, the application globally disables Basic authentication on its shared internal request handler.

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.