CVE-2021-40346

CVE-2021-40346 is an integer overflow vulnerability in HAProxy versions 2.0 through 2.5, specifically within the htx_add_header function. This flaw enables HTTP request smuggling, allowing attackers to bypass HAProxy ACLs and potentially other security controls. With a CVSS score of 7.5 (High) and an EPSS score indicating high exploitability, this vulnerability poses a significant risk due to its network-based attack vector and low attack complexity, leading to high integrity impact. While there is no known active exploitation or public exploit code (Metasploit, Nuclei, ExploitDB), the vulnerability has garnered community discussion and media coverage, suggesting awareness and potential for future exploitation.