{"id":"CVE-2019-18277","url":"https://www.cyber-defence.io/tools/cve/CVE-2019-18277","generatedAt":"2026-11-05T02:38:12.733Z","title":"In legacy mode, messages featuring a transfer-encoding header missing the \"chunked\" value were not being correctly rejected.","description":"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).","published":"2019-10-23T14:15:11.000Z","lastModified":"2026-06-17T02:24:44.000Z","status":"Modified","sourceIdentifier":"cve@mitre.org","cvss":{"version":"3.1","score":7.5,"severity":"HIGH","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N"},"cwe":["CWE-444"],"affected":["haproxy/haproxy"],"epss":{"score":0.10068,"percentile":0.95635,"date":"2026-11-03","history":[]},"kev":{"listed":false},"exploits":{"count":0,"verified":false,"firstPublished":null,"source":"Exploit-DB (https://gitlab.com/exploit-database/exploitdb)","entries":[]},"verdict":{"level":"urgent","text":"EPSS puts the probability of exploitation in the next 30 days at 10.1%, higher than 96% of all known CVEs. Patch or mitigate before the next change window."},"changes":[],"references":[{"url":"http://lists.opensuse.org/opensuse-security-announce/2019-12/msg00016.html","source":"cve@mitre.org"},{"url":"http://lists.opensuse.org/opensuse-security-announce/2019-12/msg00019.html","source":"cve@mitre.org"},{"url":"https://git.haproxy.org/?p=haproxy-2.0.git%3Ba=commit%3Bh=196a7df44d8129d1adc795da020b722614d6a581","source":"cve@mitre.org"},{"url":"https://lists.debian.org/debian-lts-announce/2022/05/msg00045.html","source":"cve@mitre.org"},{"url":"https://nathandavison.com/blog/haproxy-http-request-smuggling","tags":["Exploit","Third Party Advisory"],"source":"cve@mitre.org"},{"url":"https://usn.ubuntu.com/4174-1/","source":"cve@mitre.org"},{"url":"https://www.mail-archive.com/haproxy%40formilux.org/msg34926.html","source":"cve@mitre.org"},{"url":"http://lists.opensuse.org/opensuse-security-announce/2019-12/msg00016.html","source":"af854a3a-2127-422b-91ae-364da2661108"},{"url":"http://lists.opensuse.org/opensuse-security-announce/2019-12/msg00019.html","source":"af854a3a-2127-422b-91ae-364da2661108"},{"url":"https://git.haproxy.org/?p=haproxy-2.0.git%3Ba=commit%3Bh=196a7df44d8129d1adc795da020b722614d6a581","source":"af854a3a-2127-422b-91ae-364da2661108"},{"url":"https://lists.debian.org/debian-lts-announce/2022/05/msg00045.html","source":"af854a3a-2127-422b-91ae-364da2661108"},{"url":"https://nathandavison.com/blog/haproxy-http-request-smuggling","tags":["Exploit","Third Party Advisory"],"source":"af854a3a-2127-422b-91ae-364da2661108"},{"url":"https://usn.ubuntu.com/4174-1/","source":"af854a3a-2127-422b-91ae-364da2661108"},{"url":"https://www.mail-archive.com/haproxy%40formilux.org/msg34926.html","source":"af854a3a-2127-422b-91ae-364da2661108"}],"sources":{"nvd":"https://nvd.nist.gov/vuln/detail/CVE-2019-18277","epss":"https://www.first.org/epss/","kev":"https://www.cisa.gov/known-exploited-vulnerabilities-catalog","exploitdb":"https://www.exploit-db.com/"},"licence":"CC BY 4.0 — link back to the CVE Explorer if you publish the results; upstream data remains subject to its own terms."}