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CVE-2019-18277

A flaw was found in HAProxy before 2.0.6. In legacy mode, messages featuring a transfer-encoding...

7.5 HighFix available

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).

Attack profile

How easy it is to exploit

Attack vector
Network
Complexity
Low
Privileges needed
None
User interaction
None

What an attacker can affect

Confidentiality
None
Integrity
High
Availability
None

Exploit likelihood

10.1%Up 8.6 points since Apr 14, 2021
90%50%10%1%

What each source reports

NVD Score used 7.5

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).

Record
CVE-2019-18277
CVSS 3.1
7.5 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
CVSS 2.0
4.3 MediumAV:N/AC:M/Au:N/C:N/I:P/A:N
Weakness
CWE-444
Updated
2026-11-02
CVE List No score

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).

Record
CVE-2019-18277
Updated
2026-11-02
EUVDEUVD-2019-8066 No score

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).

Record
EUVD-2019-8066
Updated
2026-11-03
GitHub AdvisoriesGHSA-7r84-r685-grmg 7.5

A flaw was found in HAProxy before 2.0.6. In legacy mode, messages featuring a transfer-encoding...

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).

Record
GHSA-7r84-r685-grmg
CVSS 3.1
7.5 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
Weakness
CWE-444
Updated
2026-11-02
OSV 7.5

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).

Record
CVE-2019-18277
CVSS 3.1
7.5 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
Updated
2026-11-02
OSVDEBIAN-CVE-2019-18277 7.5

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).

Record
DEBIAN-CVE-2019-18277
CVSS 3.1
7.5 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
Updated
2026-11-02
Show 14 moreShow less
OSVRHSA-2020:1287 8.8

Red Hat Security Advisory: OpenShift Container Platform 3.11 security update

Record
RHSA-2020:1287
CVSS 3.1
8.8 HighCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Updated
2026-11-02
OSVRHSA-2020:1725 6.5

Red Hat Security Advisory: haproxy security, bug fix, and enhancement update

Record
RHSA-2020:1725
CVSS 3.0
6.5 MediumCVSS:3.0/AV:N/AC:H/PR:N/UI:N/S:C/C:L/I:L/A:L
Updated
2026-11-02
OSVRHSA-2020:1936 8.8

Red Hat Security Advisory: OpenShift Container Platform 4.4.3 haproxy security update

Record
RHSA-2020:1936
CVSS 3.1
8.8 HighCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Updated
2026-11-02
OSVRHSA-2020:2265 6.5

Red Hat Security Advisory: rh-haproxy18-haproxy security, bug fix, and enhancement update

Record
RHSA-2020:2265
CVSS 3.0
6.5 MediumCVSS:3.0/AV:N/AC:H/PR:N/UI:N/S:C/C:L/I:L/A:L
Updated
2026-11-02
OSVUBUNTU-CVE-2019-18277 7.5

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).

Record
UBUNTU-CVE-2019-18277
CVSS 3.1
7.5 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
Updated
2026-11-02
OSVCLSA-2026-1776336742 No score

haproxy: Fix of CVE-2019-18277

  • CVE-2019-18277: reject messages where "chunked" is missing from transfer-encoding
Record
CLSA-2026-1776336742
Updated
2026-11-02
OSVCLSA-2026-1776337242 No score

haproxy: Fix of CVE-2019-18277

  • CVE-2019-18277: reject messages where "chunked" is missing from transfer-encoding
Record
CLSA-2026-1776337242
Updated
2026-11-02
OSVopenSUSE-SU-2019:2626-1 No score

Security update for haproxy

This update for haproxy to version 2.0.10 fixes the following issues:

HAProxy was updated to 2.0.10

Security issues fixed:

  • CVE-2019-18277: Fixed a potential HTTP smuggling in messages with transfer-encoding header missing the 'chunked' (bsc#1154980).
  • Fixed an improper handling of headers which could have led to injecting LFs in H2-to-H1 transfers creating new attack space (bsc#1157712)
  • Fixed an issue where HEADER frames in idle streams are not rejected and
    thus trying to decode them HAPrpxy crashes (bsc#1157714).

Other issue addressed:

  • Macro change in the spec file (bsc#1082318)

More information regarding the release at: http://git.haproxy.org/?p=haproxy-2.0.git;a=commit;h=ac198b92d461515551b95daae20954b3053ce87e

This update was imported from the SUSE:SLE-15:Update update project.

Record
openSUSE-SU-2019:2626-1
Updated
2026-11-02
OSVopenSUSE-SU-2019:2645-1 No score

Security update for haproxy

This update for haproxy to version 2.0.10 fixes the following issues:

HAProxy was updated to 2.0.10

Security issues fixed:

  • CVE-2019-18277: Fixed a potential HTTP smuggling in messages with transfer-encoding header missing the 'chunked' (bsc#1154980).
  • Fixed an improper handling of headers which could have led to injecting LFs in H2-to-H1 transfers creating new attack space (bsc#1157712)
  • Fixed an issue where HEADER frames in idle streams are not rejected and
    thus trying to decode them HAPrpxy crashes (bsc#1157714).

Other issue addressed:

  • Macro change in the spec file (bsc#1082318)

More information regarding the release at: http://git.haproxy.org/?p=haproxy-2.0.git;a=commit;h=ac198b92d461515551b95daae20954b3053ce87e

This update was imported from the SUSE:SLE-15-SP1:Update update project.

Record
openSUSE-SU-2019:2645-1
Updated
2026-11-02
OSVopenSUSE-SU-2024:10839-1 No score

haproxy-2.4.4+git0.acb1d0bea-1.2 on GA media

These are all security issues fixed in the haproxy-2.4.4+git0.acb1d0bea-1.2 package on the GA media of openSUSE Tumbleweed.

Record
openSUSE-SU-2024:10839-1
Updated
2026-11-02
OSVSUSE-SU-2019:3125-1 No score

Security update for haproxy

This update for haproxy to version 2.0.10 fixes the following issues:

HAProxy was updated to 2.0.10

Security issues fixed:

  • CVE-2019-18277: Fixed a potential HTTP smuggling in messages with transfer-encoding header missing the 'chunked' (bsc#1154980).
  • Fixed an improper handling of headers which could have led to injecting LFs in H2-to-H1 transfers creating new attack space (bsc#1157712)
  • Fixed an issue where HEADER frames in idle streams are not rejected and
    thus trying to decode them HAPrpxy crashes (bsc#1157714).

Other issue addressed:

  • Macro change in the spec file (bsc#1082318)

More information regarding the release at: http://git.haproxy.org/?p=haproxy-2.0.git;a=commit;h=ac198b92d461515551b95daae20954b3053ce87e

Record
SUSE-SU-2019:3125-1
Updated
2026-11-02
OSVSUSE-SU-2019:3126-1 No score

Security update for haproxy

This update for haproxy to version 2.0.10 fixes the following issues:

HAProxy was updated to 2.0.10

Security issues fixed:

  • CVE-2019-18277: Fixed a potential HTTP smuggling in messages with transfer-encoding header missing the 'chunked' (bsc#1154980).
  • Fixed an improper handling of headers which could have led to injecting LFs in H2-to-H1 transfers creating new attack space (bsc#1157712)
  • Fixed an issue where HEADER frames in idle streams are not rejected and
    thus trying to decode them HAPrpxy crashes (bsc#1157714).

Other issue addressed:

  • Macro change in the spec file (bsc#1082318)

More information regarding the release at: http://git.haproxy.org/?p=haproxy-2.0.git;a=commit;h=ac198b92d461515551b95daae20954b3053ce87e

Record
SUSE-SU-2019:3126-1
Updated
2026-11-02
OSVSUSE-SU-2019:3288-1 No score

Security update for haproxy

This update for haproxy fixes the following issues:

  • CVE-2019-18277: Fixed HTTP smuggling in messages with transfer-encoding header missing the 'chunked' value (bsc#1154980).
Record
SUSE-SU-2019:3288-1
Updated
2026-11-02
OSVUSN-4174-1 No score

haproxy vulnerability

It was discovered that HAproxy incorrectly handled certain HTTP requests. An attacker could possibly use this issue to a privilege escalation (Request Smuggling).

Record
USN-4174-1
Updated
2026-11-02

Affected products

Affected packages

Affected packages
PackageAffectedFixed
haproxy
TuxCare:OracleLinux:6
 before 1.5.18-1.el6.tuxcare.els2
1.5.18-1.el6.tuxcare.els2
haproxy
TuxCare:CentOS:6
 before 1.5.18-1.el6.tuxcare.els2
1.5.18-1.el6.tuxcare.els2
haproxy
Debian:12
 before 2.0.6-1
2.0.6-1
haproxy
Debian:13
 before 2.0.6-1
2.0.6-1
haproxy
Debian:14
 before 2.0.6-1
2.0.6-1
haproxy
Debian:9
From an advisory covering 3 CVEs
 before 1.7.5-2+deb9u1, plus listed versions
1.7.5-2
1.7.5-2+deb9u1
haproxy
Red Hat:openshift:3.11::el7
From an advisory covering 3 CVEs
 before 0:1.8.23-3.el7
0:1.8.23-3.el7
haproxy-debuginfo
Red Hat:openshift:3.11::el7
From an advisory covering 3 CVEs
 before 0:1.8.23-3.el7
0:1.8.23-3.el7
haproxy18
Red Hat:openshift:3.11::el7
From an advisory covering 3 CVEs
 before 0:1.8.23-3.el7
0:1.8.23-3.el7
haproxy
Red Hat:enterprise_linux:8::appstream
From an advisory covering 2 CVEs
 before 0:1.8.23-3.el8
0:1.8.23-3.el8
Show 28 moreShow less
Affected packages
PackageAffectedFixed
haproxy-debuginfo
Red Hat:enterprise_linux:8::appstream
From an advisory covering 2 CVEs
 before 0:1.8.23-3.el8
0:1.8.23-3.el8
haproxy-debugsource
Red Hat:enterprise_linux:8::appstream
From an advisory covering 2 CVEs
 before 0:1.8.23-3.el8
0:1.8.23-3.el8
haproxy
Red Hat:openshift:4.4::el7
From an advisory covering 3 CVEs
 before 0:2.0.13-3.el7
0:2.0.13-3.el7
haproxy-debuginfo
Red Hat:openshift:4.4::el7
From an advisory covering 3 CVEs
 before 0:2.0.13-3.el7
0:2.0.13-3.el7
haproxy20
Red Hat:openshift:4.4::el7
From an advisory covering 3 CVEs
 before 0:2.0.13-3.el7
0:2.0.13-3.el7
haproxy
Red Hat:openshift:4.4::el8
From an advisory covering 3 CVEs
 before 0:2.0.13-3.el8
0:2.0.13-3.el8
haproxy-debugsource
Red Hat:openshift:4.4::el8
From an advisory covering 3 CVEs
 before 0:2.0.13-3.el8
0:2.0.13-3.el8
haproxy20
Red Hat:openshift:4.4::el8
From an advisory covering 3 CVEs
 before 0:2.0.13-3.el8
0:2.0.13-3.el8
haproxy20-debuginfo
Red Hat:openshift:4.4::el8
From an advisory covering 3 CVEs
 before 0:2.0.13-3.el8
0:2.0.13-3.el8
rh-haproxy18-haproxy
Red Hat:rhel_software_collections:3::el7
From an advisory covering 2 CVEs
 before 0:1.8.24-2.el7
0:1.8.24-2.el7
rh-haproxy18-haproxy-debuginfo
Red Hat:rhel_software_collections:3::el7
From an advisory covering 2 CVEs
 before 0:1.8.24-2.el7
0:1.8.24-2.el7
rh-haproxy18-haproxy-syspaths
Red Hat:rhel_software_collections:3::el7
From an advisory covering 2 CVEs
 before 0:1.8.24-2.el7
0:1.8.24-2.el7
haproxy
SUSE:Linux Enterprise High Availability Extension 15
 before 2.0.10+git0.ac198b92-3.15.1
2.0.10+git0.ac198b92-3.15.1
haproxy
SUSE:Linux Enterprise High Availability Extension 15 SP1
 before 2.0.10+git0.ac198b92-8.8.1
2.0.10+git0.ac198b92-8.8.1
haproxy
SUSE:HPE Helion OpenStack 8
 before 1.6.11-11.3.1
1.6.11-11.3.1
haproxy
SUSE:OpenStack Cloud 7
 before 1.6.11-11.3.1
1.6.11-11.3.1
haproxy
SUSE:OpenStack Cloud 8
 before 1.6.11-11.3.1
1.6.11-11.3.1
haproxy
SUSE:OpenStack Cloud 9
 before 1.6.11-11.3.1
1.6.11-11.3.1
haproxy
SUSE:OpenStack Cloud Crowbar 8
 before 1.6.11-11.3.1
1.6.11-11.3.1
haproxy
SUSE:OpenStack Cloud Crowbar 9
 before 1.6.11-11.3.1
1.6.11-11.3.1
haproxy
SUSE:Linux Enterprise High Availability Extension 12 SP3
 before 1.6.11-11.3.1
1.6.11-11.3.1
haproxy
SUSE:Linux Enterprise High Availability Extension 12 SP4
 before 1.6.11-11.3.1
1.6.11-11.3.1
haproxy
SUSE:Linux Enterprise High Availability Extension 12 SP5
 before 1.6.11-11.3.1
1.6.11-11.3.1
haproxy
Ubuntu:16.04:LTS
 before 1.6.3-1ubuntu0.3, plus listed versions
1.5.14-11.5.15-11.6.2-11.6.2-21.6.2-2ubuntu1
Show 4 moreShow less
1.6.2-2ubuntu31.6.3-11.6.3-1ubuntu0.11.6.3-1ubuntu0.2
1.6.3-1ubuntu0.3
haproxy
Ubuntu:18.04:LTS
 before 1.8.8-1ubuntu0.7, plus listed versions
1.7.9-1ubuntu11.7.9-1ubuntu21.8.4-11.8.7-11.8.8-1
Show 5 moreShow less
1.8.8-1ubuntu0.11.8.8-1ubuntu0.21.8.8-1ubuntu0.31.8.8-1ubuntu0.41.8.8-1ubuntu0.6
1.8.8-1ubuntu0.7
haproxy
openSUSE:Leap 15.0
 before 2.0.10+git0.ac198b92-lp150.2.16.1
2.0.10+git0.ac198b92-lp150.2.16.1
haproxy
openSUSE:Leap 15.1
 before 2.0.10+git0.ac198b92-lp151.2.6.1
2.0.10+git0.ac198b92-lp151.2.6.1
haproxy
openSUSE:Tumbleweed
From an advisory covering 9 CVEs
 before 2.4.4+git0.acb1d0bea-1.2
2.4.4+git0.acb1d0bea-1.2

History

History
RecordedChangedSources
affected, facts
aliasesEUVD
first indexedCVE List, GitHub Advisories, NVD, OSV

Dates are when Every CVE recorded each change. Upstream dates may differ.

In short

CVE-2019-18277 is a high vulnerability (CVSS 7.5) in Haproxy, published October 23, 2019. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 10.1%, the 95th percentile. Fixed in haproxy 1.5.18-1.el6.tuxcare.els2.

References

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