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Fencer Vulns
high 7.5

CVE-2019-18277 in the critical feed json

A flaw was found in HAProxy before 2.0.6.

published 2019-10-23 7 y ago modified 2026-06-17 4 mo ago also EUVD-2019-8066

cvss
7.5
version 3.1, NVD
cisa kev
Not listed
not in CISA's catalog
epss
10.1%
EPSS 10.1% chance of exploitation in 30 days, percentile 95%
public exploits
0
none known

Summary

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).

Patch / fix

  • haproxy haproxy 2.0.6
  • haproxy Debian 14, Debian 13, Debian 12 2.0.6-1

debian advisories DEBIAN-CVE-2019-18277

  • haproxy Ubuntu 16.04 LTS 1.6.3-1ubuntu0.3
  • haproxy Ubuntu 18.04 LTS 1.8.8-1ubuntu0.7

ubuntu advisories UBUNTU-CVE-2019-18277

Ubuntu security data © Canonical Ltd., from https://github.com/canonical/ubuntu-security-notices via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

  • haproxy openshift 4.4 2.0.13-3.el7
  • haproxy openshift 4.4 2.0.13-3.el8
  • haproxy20 openshift 4.4 2.0.13-3.el7
  • haproxy20 openshift 4.4 2.0.13-3.el8
  • haproxy openshift 3.11 1.8.23-3.el7
  • haproxy18 openshift 3.11 1.8.23-3.el7
  • rh-haproxy18-haproxy RHEL 3 SOFTWARE_COLLECTIONS 1.8.24-2.el7
  • rh-haproxy18-haproxy-syspaths RHEL 3 SOFTWARE_COLLECTIONS 1.8.24-2.el7

red hat advisories RHSA-2020:1936RHSA-2020:1287RHSA-2020:2265RHSA-2020:1725

  • haproxy SLE High Availability Extension 12 SP5, SLE High Availability Extension 12 SP4, SLE High Availability Extension 12 SP3 +6 more 1.6.11-11.3.1
  • haproxy SLE High Availability Extension 15 SP1 2.0.10+git0.ac198b92-8.8.1
  • haproxy SLE High Availability Extension 15 2.0.10+git0.ac198b92-3.15.1

suse advisories SUSE-SU-2019:3288-1SUSE-SU-2019:3126-1SUSE-SU-2019:3125-1

  • haproxy openSUSE Tumbleweed 2.4.4+git0.acb1d0bea-1.2
  • haproxy openSUSE Leap 15.1 2.0.10+git0.ac198b92-lp151.2.6.1
  • haproxy openSUSE Leap 15.0 2.0.10+git0.ac198b92-lp150.2.16.1

opensuse advisories openSUSE-SU-2024:10839-1openSUSE-SU-2019:2645-1openSUSE-SU-2019:2626-1

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2019-18277 updated cvss 6.5

haproxy: HTTP request smuggling issue with transfer-encoding header containing an obfuscated "chunked" value

  • Red Hat OpenShift Container Platform 3.9 haproxy, haproxy18 Red Hat OpenShift Container Platform 3.10 haproxy, haproxy18
    affected: workaround, no fix planned “Will not fix”
  • Red Hat Enterprise Linux AppStream (v. 8) haproxy 1.8.23-3.el8
    fixed: vendor fix RHSA-2020:1725
  • Red Hat OpenShift Container Platform 3.11 haproxy 1.8.23-3.el7, haproxy18 1.8.23-3.el7
    fixed: vendor fix RHSA-2020:1287
  • Red Hat OpenShift Container Platform 4.4 haproxy 2.0.13-3.el7, haproxy 2.0.13-3.el8, haproxy20 2.0.13-3.el7, haproxy20 2.0.13-3.el8
    fixed: vendor fix RHSA-2020:1936
  • Red Hat Software Collections for Red Hat Enterprise Linux Server (v. 7) rh-haproxy18-haproxy 1.8.24-2.el7, rh-haproxy18-haproxy-syspaths 1.8.24-2.el7 Red Hat Software Collections for Red Hat Enterprise Linux Server EUS (v. 7.6) rh-haproxy18-haproxy 1.8.24-2.el7, rh-haproxy18-haproxy-syspaths 1.8.24-2.el7 Red Hat Software Collections for Red Hat Enterprise Linux Server EUS (v. 7.7) rh-haproxy18-haproxy 1.8.24-2.el7, rh-haproxy18-haproxy-syspaths 1.8.24-2.el7 Red Hat Software Collections for Red Hat Enterprise Linux Workstation (v. 7) rh-haproxy18-haproxy 1.8.24-2.el7, rh-haproxy18-haproxy-syspaths 1.8.24-2.el7
    fixed: vendor fix RHSA-2020:2265
  • Red Hat Enterprise Linux 6 haproxy Red Hat Enterprise Linux 7 haproxy
    not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

Exploit prediction

10.07% chance of exploitation in the next 30 days, higher than 95% of all scored CVEs (FIRST EPSS, 2026-11-08).

Exploits and checks

  • nathandavison.com https://nathandavison.com/blog/haproxy-http-request-smuggling referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by version score vector
NVD 3.1 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
NVD 2.0 4.3 AV:N/AC:M/Au:N/C:N/I:P/A:N

Classification

Weakness
  • CWE-444 Inconsistent Interpretation of HTTP Requests

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.