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No exploitation reportedFix available

CVE-2019-18277

No exploitation reported by the sources we read.

  • Published2019-10-23
  • Fixed in2.0.6
  • WeaknessCWE-444

Am I affected?

With a domain, we read the version its public headers and pages expose. A distribution build can carry the fix under an older number.

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).

Timeline

dates in UTC
  1. 2019-10-2314:15CVE publishedNVD

Versions per branch

NVD
HAProxy
BranchAffectedFixed in
2.0< 2.0.62.0.6

as publishedRanges as NVD and OSV publish them; a distribution’s build can be fixed under an older number.

Distribution builds and vendor advisories

Packages from OSV.dev and products from the vendors' CSAF advisories.

version not verifiedVersions not verified: read as OSV.dev and the vendors publish them, not checked against each vendor's release list.

Packages

  • haproxyUbuntu:18.04:LTSall versions · fixed in 1.8.8-1ubuntu0.7
  • haproxyUbuntu:16.04:LTSall versions · fixed in 1.6.3-1ubuntu0.3
  • haproxyTuxCare:OracleLinux:6all versions · fixed in 1.5.18-1.el6.tuxcare.els2
  • haproxyTuxCare:CentOS:6all versions · fixed in 1.5.18-1.el6.tuxcare.els2
  • haproxySUSE:OpenStack Cloud Crowbar 9all versions · fixed in 1.6.11-11.3.1
  • haproxySUSE:OpenStack Cloud Crowbar 8all versions · fixed in 1.6.11-11.3.1
  • haproxySUSE:OpenStack Cloud 9all versions · fixed in 1.6.11-11.3.1
  • haproxySUSE:OpenStack Cloud 8all versions · fixed in 1.6.11-11.3.1

19 more package ranges on OSV.dev

Vendor advisories

  • CVE-2019-18277 Red Hat Product Security41 products fixed · 4 known affected

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

    haproxy.src as a component of Red Hat OpenShift Container Platform 3.10 · haproxy18 as a component of Red Hat OpenShift Container Platform 3.10 · haproxy.src as a component of Red Hat OpenShift Container Platform 3.9 · +1 more

  • RHSA-2020:2265 Red Hat Product Security16 products fixed

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

  • RHSA-2020:1936 Red Hat Product Security7 products fixed

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

  • RHSA-2020:1725 Red Hat Product Security13 products fixed

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

  • RHSA-2020:1287 Red Hat Product Security5 products fixed

    Red Hat Security Advisory: OpenShift Container Platform 3.11 security update

Full record on NVD

Fix

  1. Update HAProxy to 2.0.6
  2. Vendor fix Red Hat Product Security RHSA-2020:2265 · 16 productsFor details on how to apply this update, which includes the changes described in this advisory, refer to: https://access.redhat.com/articles/11258
  3. Vendor fix Red Hat Product Security RHSA-2020:1936 · 7 productsFor OpenShift Container Platform 4.4 see the following documentation, which will be updated shortly for release 4.4.3, for important instructions on how to upgrade your cluster and fully apply this asynchronous errata update: https://docs.openshift.com/container-platform/4.4/release_notes/ocp-4-4-…
  4. Vendor fix Red Hat Product Security RHSA-2020:1287 · 5 productsBefore applying this update, ensure all previously released errata relevant to your system is applied. See the following documentation, which will be updated shortly for release 3.11.200, for important instructions on how to upgrade your cluster and fully apply this asynchronous errata update: ht…
  5. Workaround from the vendor Red Hat Product Security RHSA-2020:2265 · 16 products- Reconsider the use of `http-reuse always` if possible - Disable HTTP Keep-Alive (also called HTTP Connection reuse) in the backend - Fix the backend server to correctly parse Transfer-Encoding/Content-Length headers
  6. No fix planned, says the vendor Red Hat Product Security CVE-2019-18277 · 4 productsWill not fix

Detection

Nuclei template
none so far
ProjectDiscovery
Exploit-DB
no entry
Exploit-DB
Proof of concept
Metasploit modules
none listed
Metasploit Framework

Sources

Identifiers

Technical details

CVSS v3 Vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
Published
2019-10-23
Last Modified
2026-06-17
NVD status
Modified
GitHub Advisory
GHSA-7r84-r685-grmg

Frequently asked questions

What is 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).

Is CVE-2019-18277 actively exploited?

Active exploitation of CVE-2019-18277 has not been confirmed. Its EPSS score was 10.1% on 2026-11-08, the estimated probability of exploitation in the next 30 days.

What is the CVSS score for CVE-2019-18277?

CVE-2019-18277 has a CVSS v3 base score of 7.5 (HIGH severity), with vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N.

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