CVE-2019-18277: Haproxy

High severity, CVSS 7.5. EPSS: 10.1% chance of exploitation in the next 30 days.

A flaw was found in HAProxy before 2.0.6. In legacy mode, messages featuring a transfer-encoding header missing the "chunked" value were not being correctly rejected. The impact was limited but if combined with the "http-reuse always" setting, it could be used to help construct an HTTP request smuggling attack against a vulnerable component employing a lenient parser that would ignore the content-length header as soon as it saw a transfer-encoding one (even if not entirely valid according to the specification).

Affected products

• Haproxy Haproxy: before 2.0.6 (fixed in 2.0.6)

Published 2019-10-23. Last modified 2026-06-17.