Vulnerability in Haproxy
CVE-2019-18277
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).
Vulnerability class: HTTP Request Smuggling
Published · last modified .
CVSS v3 metric
CVSS v3 base score 7.5 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N.
EPSS exploit prediction
EPSS: 0.100 (95.5th percentile), scored .
Moderate probability of exploitation in the next 30 days — watch for active exploitation reports. 95th percentile — 95.5% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.100 · newest: 0.100 · change: 0.000
Affected products
Weakness classification (CWE)
Public proof-of-concept exploits
References
- www.mail-archive.com/haproxy@formilux.org/msg34926.html
- nathandavison.com/blog/haproxy-http-request-smuggling (Exploit, Third Party Advisory)
- git.haproxy.org/
- usn.ubuntu.com/4174-1/ (vendor-advisory)
- lists.opensuse.org/opensuse-security-announce/2019-12/msg00016.html (vendor-advisory)
- lists.opensuse.org/opensuse-security-announce/2019-12/msg00019.html (vendor-advisory)
- lists.debian.org/debian-lts-announce/2022/05/msg00045.html (mailing-list)
Frequently asked questions
- What is CVE-2019-18277?
- CVE-2019-18277 is a high-severity vulnerability in Haproxy, classified under Inconsistent Interpretation of HTTP Requests (HTTP Request/Response Smuggling). CVSS score: 7.5/10. Published 2019-10-23.
- How severe is CVE-2019-18277?
- High severity. CVSS v3 base score is 7.5 out of 10.
- Is CVE-2019-18277 known to be exploited?
- 6 public proof-of-concept repositories are indexed. Not currently listed in the CISA KEV catalog.