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Haproxy vulnerabilities

Known CVEs affecting Haproxy products, prioritized by severity, with SEC.co remediation and detection guidance.

2 published vulnerabilities

• CVE-2026-55203HIGH 7.5

  HAProxy versions up to 3.4.0 contain an integer overflow bug in how it parses FastCGI protocol frames from backend servers. When a malicious or compromised FastCGI backend sends specially crafted messages with maximum content length (65535 bytes) plus padding, an internal counter wraps around to zero, causing HAProxy to misinterpret where the next message begins. This can lead to request routing errors, response smuggling attacks, or memory corruption. The flaw requires an attacker to control or compromise a FastCGI backend server connected to the HAProxy instance.

• CVE-2026-55204HIGH 7.5

  HAProxy versions through 3.4.0 contain a vulnerability that allows attackers to crash HAProxy worker processes by exploiting how the software handles HTTP/2 header compression under memory constraints. When HAProxy's internal memory pool becomes full, the software fails to properly check whether a memory cleanup operation succeeded before attempting to use its results, leading to a crash. An attacker can remotely trigger this condition by sending specially crafted HTTP/2 requests, causing denial of service without needing authentication or special privileges.