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CVE-2021-40346

An integer overflow exists in HAProxy 2.0 through 2.5 in the htx_add_header() can be exploited to...

7.5 HighPublic exploitFix available

An integer overflow exists in HAProxy 2.0 through 2.5 in htx_add_header that can be exploited to perform an HTTP request smuggling attack, allowing an attacker to bypass all configured http-request HAProxy ACLs and possibly other ACLs.

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

58.8%Up 57.4 points since Sep 9, 2021
90%50%10%1%

What each source reports

NVD Score used 7.5

An integer overflow exists in HAProxy 2.0 through 2.5 in htx_add_header that can be exploited to perform an HTTP request smuggling attack, allowing an attacker to bypass all configured http-request HAProxy ACLs and possibly other ACLs.

Record
CVE-2021-40346
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
5.0 MediumAV:N/AC:L/Au:N/C:N/I:P/A:N
Weakness
CWE-190
Updated
2026-11-02
CVE List No score

An integer overflow exists in HAProxy 2.0 through 2.5 in htx_add_header that can be exploited to perform an HTTP request smuggling attack, allowing an attacker to bypass all configured http-request HAProxy ACLs and possibly other ACLs.

Record
CVE-2021-40346
Updated
2026-11-02
EUVDEUVD-2021-27525 No score

An integer overflow exists in HAProxy 2.0 through 2.5 in htx_add_header that can be exploited to perform an HTTP request smuggling attack, allowing an attacker to bypass all configured http-request HAProxy ACLs and possibly other ACLs.

Record
EUVD-2021-27525
Updated
2026-11-03
GitHub AdvisoriesGHSA-jwmg-q4wv-f75h No score

An integer overflow exists in HAProxy 2.0 through 2.5 in the htx_add_header() can be exploited to...

An integer overflow exists in HAProxy 2.0 through 2.5 in the htx_add_header() can be exploited to perform an HTTP request smuggling attack, allowing an attacker to bypass all configured http-request HAProxy ACLs and possibly other ACLs.

Record
GHSA-jwmg-q4wv-f75h
Weakness
CWE-190
Updated
2026-11-02
OSV 7.5

An integer overflow exists in HAProxy 2.0 through 2.5 in htx_add_header that can be exploited to perform an HTTP request smuggling attack, allowing an attacker to bypass all configured http-request HAProxy ACLs and possibly other ACLs.

Record
CVE-2021-40346
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-2021-40346 7.5

An integer overflow exists in HAProxy 2.0 through 2.5 in htx_add_header that can be exploited to perform an HTTP request smuggling attack, allowing an attacker to bypass all configured http-request HAProxy ACLs and possibly other ACLs.

Record
DEBIAN-CVE-2021-40346
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
OSVOESA-2021-1367 7.5

haproxy security update

HAProxy is a free, very fast and reliable solution offering high availability, load balancing, and proxying for TCP and HTTP-based applications. It is particularly suited for very high traffic web sites and powers quite a number of the world's most visited ones.

Security Fix(es):

An integer overflow exists in HAProxy 2.0 through 2.5 in htx_add_header that can be exploited to perform an HTTP request smuggling attack, allowing an attacker to bypass all configured http-request HAProxy ACLs and possibly other ACLs.(CVE-2021-40346)

Record
OESA-2021-1367
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
OSVRHSA-2021:4118 7.5

Red Hat Security Advisory: OpenShift Container Platform 4.9.6 packages and security update

Record
RHSA-2021:4118
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
OSVRHSA-2021:5208 7.5

Red Hat Security Advisory: OpenShift Container Platform 4.8.25 security update

Record
RHSA-2021:5208
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
OSVRHSA-2022:0024 7.5

Red Hat Security Advisory: OpenShift Container Platform 4.6.53 security update

Record
RHSA-2022:0024
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
OSVRHSA-2022:0114 7.5

Red Hat Security Advisory: OpenShift Container Platform 4.7.41 security update

Record
RHSA-2022:0114
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
OSVUBUNTU-CVE-2021-40346 7.5

An integer overflow exists in HAProxy 2.0 through 2.5 in htx_add_header that can be exploited to perform an HTTP request smuggling attack, allowing an attacker to bypass all configured http-request HAProxy ACLs and possibly other ACLs.

Record
UBUNTU-CVE-2021-40346
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
OSVBIT-haproxy-2021-40346 No score

An integer overflow exists in HAProxy 2.0 through 2.5 in htx_add_header that can be exploited to perform an HTTP request smuggling attack, allowing an attacker to bypass all configured http-request HAProxy ACLs and possibly other ACLs.

Record
BIT-haproxy-2021-40346
Updated
2026-11-02
OSVopenSUSE-SU-2021:1329-1 No score

Security update for haproxy

This update for haproxy fixes the following issues:

  • CVE-2021-40346: Fixed request smuggling vulnerability in HTX (bsc#1189877).

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

Record
openSUSE-SU-2021:1329-1
Updated
2026-11-02
OSVopenSUSE-SU-2021:2975-1 No score

Security update for haproxy

This update for haproxy fixes the following issues:

  • CVE-2021-40346: Fixed request smuggling vulnerability in HTX (bsc#1189877).
Record
openSUSE-SU-2021:2975-1
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-2021:2975-1 No score

Security update for haproxy

This update for haproxy fixes the following issues:

  • CVE-2021-40346: Fixed request smuggling vulnerability in HTX (bsc#1189877).
Record
SUSE-SU-2021:2975-1
Updated
2026-11-02
OSVSUSE-SU-2021:3257-1 No score

Security update for haproxy

This update for haproxy fixes the following issues:

  • CVE-2021-40346: Fixed request smuggling vulnerability in HTX (bsc#1189877).
Record
SUSE-SU-2021:3257-1
Updated
2026-11-02
OSVSUSE-SU-2021:3258-1 No score

Security update for haproxy

This update for haproxy fixes the following issues:

  • CVE-2021-40346: Fixed request smuggling vulnerability in HTX (bsc#1189877).
Record
SUSE-SU-2021:3258-1
Updated
2026-11-02
OSVUSN-5063-1 No score

haproxy vulnerabilities

Ori Hollander discovered that HAProxy incorrectly handled HTTP header name length encoding. A remote attacker could possibly use this issue to inject a duplicate content-length header and perform request smuggling attacks.

Record
USN-5063-1
Updated
2026-11-02

Affected products

Affected packages

Affected packages
PackageAffectedFixed
haproxy
Bitnami
 2.0.0 up to 2.0.25, 2.2.0 up to 2.2.17, 2.3.0 up to 2.3.14, 2.4.0 up to 2.4.4
2.0.252.2.172.3.142.4.4
haproxy
Debian:12
 before 2.2.16-3
2.2.16-3
haproxy
Debian:13
 before 2.2.16-3
2.2.16-3
haproxy
Debian:14
 before 2.2.16-3
2.2.16-3
haproxy
Debian:11
 before 2.2.9-2+deb11u2, plus listed versions
2.2.9-22.2.9-2+deb11u12.2.9-2+deb11u1~bpo10+12.2.9-2+deb11u2~bpo10+1
2.2.9-2+deb11u2
haproxy
openEuler:20.03-LTS-SP1
 before 2.2.16-2.oe1
2.2.16-2.oe1
haproxy
openEuler:20.03-LTS-SP2
 before 2.2.16-2.oe1
2.2.16-2.oe1
haproxy
Red Hat:openshift:4.9::el8
From an advisory covering 4 CVEs
 before 0:2.2.15-2.el8
0:2.2.15-2.el8
haproxy-debugsource
Red Hat:openshift:4.9::el8
From an advisory covering 4 CVEs
 before 0:2.2.15-2.el8
0:2.2.15-2.el8
haproxy
Red Hat:openshift:4.8::el7
From an advisory covering 4 CVEs
 before 0:2.2.13-2.el7
0:2.2.13-2.el7
Show 26 moreShow less
Affected packages
PackageAffectedFixed
haproxy-debuginfo
Red Hat:openshift:4.8::el7
From an advisory covering 4 CVEs
 before 0:2.2.13-2.el7
0:2.2.13-2.el7
haproxy
Red Hat:openshift:4.8::el8
From an advisory covering 4 CVEs
 before 0:2.2.13-2.el8
0:2.2.13-2.el8
haproxy-debugsource
Red Hat:openshift:4.8::el8
From an advisory covering 4 CVEs
 before 0:2.2.13-2.el8
0:2.2.13-2.el8
haproxy
Red Hat:openshift:4.6::el7
From an advisory covering 2 CVEs
 before 0:2.0.16-2.el7
0:2.0.16-2.el7
haproxy-debuginfo
Red Hat:openshift:4.6::el7
From an advisory covering 2 CVEs
 before 0:2.0.16-2.el7
0:2.0.16-2.el7
haproxy20
Red Hat:openshift:4.6::el7
From an advisory covering 2 CVEs
 before 0:2.0.16-2.el7
0:2.0.16-2.el7
haproxy
Red Hat:openshift:4.6::el8
From an advisory covering 2 CVEs
 before 0:2.0.16-4.el8
0:2.0.16-4.el8
haproxy-debugsource
Red Hat:openshift:4.6::el8
From an advisory covering 2 CVEs
 before 0:2.0.16-4.el8
0:2.0.16-4.el8
haproxy20
Red Hat:openshift:4.6::el8
From an advisory covering 2 CVEs
 before 0:2.0.16-4.el8
0:2.0.16-4.el8
haproxy20-debuginfo
Red Hat:openshift:4.6::el8
From an advisory covering 2 CVEs
 before 0:2.0.16-4.el8
0:2.0.16-4.el8
haproxy
Red Hat:openshift:4.7::el7
From an advisory covering 2 CVEs
 before 0:2.0.19-2.el7
0:2.0.19-2.el7
haproxy-debuginfo
Red Hat:openshift:4.7::el7
From an advisory covering 2 CVEs
 before 0:2.0.19-2.el7
0:2.0.19-2.el7
haproxy20
Red Hat:openshift:4.7::el7
From an advisory covering 2 CVEs
 before 0:2.0.19-2.el7
0:2.0.19-2.el7
haproxy
Red Hat:openshift:4.7::el8
From an advisory covering 2 CVEs
 before 0:2.0.19-2.el8
0:2.0.19-2.el8
haproxy-debugsource
Red Hat:openshift:4.7::el8
From an advisory covering 2 CVEs
 before 0:2.0.19-2.el8
0:2.0.19-2.el8
haproxy20
Red Hat:openshift:4.7::el8
From an advisory covering 2 CVEs
 before 0:2.0.19-2.el8
0:2.0.19-2.el8
haproxy20-debuginfo
Red Hat:openshift:4.7::el8
From an advisory covering 2 CVEs
 before 0:2.0.19-2.el8
0:2.0.19-2.el8
haproxy
SUSE:Linux Enterprise High Availability Extension 15 SP2
 before 2.0.14-11.11.1
2.0.14-11.11.1
haproxy
SUSE:Linux Enterprise High Availability Extension 15 SP3
 before 2.0.14-11.11.1
2.0.14-11.11.1
haproxy
SUSE:Linux Enterprise High Availability Extension 15 SP1
 before 2.0.14-8.23.1
2.0.14-8.23.1
haproxy
SUSE:Linux Enterprise High Availability Extension 15
 before 2.0.14-3.31.1
2.0.14-3.31.1
haproxy
Ubuntu:20.04:LTS
 before 2.0.13-2ubuntu0.3, plus listed versions
2.0.5-12.0.8-12.0.9-12.0.10-12.0.10-1ubuntu1
Show 6 moreShow less
2.0.11-1ubuntu12.0.12-1ubuntu22.0.13-1ubuntu22.0.13-22.0.13-2ubuntu0.12.0.13-2ubuntu0.2
2.0.13-2ubuntu0.3
haproxy
Ubuntu:22.04:LTS
 before 2.2.9-2ubuntu2
2.2.9-2ubuntu2
haproxy
openSUSE:Leap 15.2
 before 2.0.14-lp152.2.6.1
2.0.14-lp152.2.6.1
haproxy
openSUSE:Leap 15.3
 before 2.0.14-11.11.1
2.0.14-11.11.1
haproxy
openSUSE:Tumbleweed
From an advisory covering 9 CVEs
 before 2.4.4+git0.acb1d0bea-1.2
2.4.4+git0.acb1d0bea-1.2

Public exploits

Links only. Every CVE stores no exploit code.

Public exploits
SourceLinkDate
PoC in GitHubknqyf263/CVE-2021-403462021-09-08
PoC in GitHubalikarimi999/CVE-2021-403462021-09-10
PoC in GitHubdonky16/CVE-2021-40346-POC2021-09-10
PoC in GitHubVulnmachines/HAProxy_CVE-2021-403462021-11-08
PoC in GitHubalexOarga/CVE-2021-403462022-01-24
PoC in GitHubBoianEduard/CVE-2021-403462025-12-21
PoC in GitHubjmg0929/CVE-2021-403462026-07-08

History

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

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

In short

CVE-2021-40346 is a high vulnerability (CVSS 7.5) in Haproxy, published September 7, 2021. Public exploit code exists. EPSS puts the chance of exploitation in the next 30 days at 58.8%, the 99th percentile. Fixed in haproxy 2.0.25.

References

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