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Fencer Vulns
high 7.5

CVE-2023-0836 json

An information leak vulnerability was discovered in HAProxy 2.1, 2.2 before 2.2.27, 2.3, 2.4 before 2.4.21, 2.5 before 2.5.11, 2.6 before 2…

published 2023-03-29 3 y ago modified 2026-06-17 4 mo ago also BIT-haproxy-2023-0836 , EUVD-2023-12837

cvss
7.5
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
1.2%
EPSS 1.2% chance of exploitation in 30 days, percentile 68%
public exploits
0
none known

Summary

An information leak vulnerability was discovered in HAProxy 2.1, 2.2 before 2.2.27, 2.3, 2.4 before 2.4.21, 2.5 before 2.5.11, 2.6 before 2.6.8, 2.7 before 2.7.1. There are 5 bytes left uninitialized in the connection buffer when encoding the FCGI_BEGIN_REQUEST record. Sensitive data may be disclosed to configured FastCGI backends in an unexpected way.

Patch / fix

  • bitnami haproxy 2.1.1, 2.2.27, 2.3.1, 2.4.22, 2.5.12, 2.6.9, 2.7.1
  • haproxy haproxy 2.2.27
  • haproxy Debian 14, Debian 13, Debian 12 2.6.8-1

debian advisories DEBIAN-CVE-2023-0836

  • haproxy Ubuntu 22.04 LTS 2.4.18-0ubuntu1.3

ubuntu advisories UBUNTU-CVE-2023-0836

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 RHEL 9 2.4.22-1.el9

red hat advisories RHSA-2023:6496

  • haproxy AlmaLinux 9 2.4.22-1.el9

almalinux advisories ALSA-2023:6496

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-2023-0836 updated cvss 7.5

haproxy: data leak via fcgi requests

  • Red Hat Ceph Storage 5 haproxy, haproxy22
    affected: no fix available
  • Red Hat Enterprise Linux 7 haproxy Red Hat OpenShift Container Platform 3.11 haproxy, haproxy18
    affected: no fix planned “Out of support scope”
  • Red Hat OpenShift Container Platform 4 haproxy, haproxy18, haproxy20, haproxy22, haproxy26, haproxy28 Red Hat Software Collections rh-haproxy18-haproxy, rh-haproxy18-haproxy-syspaths
    affected: no fix planned “Will not fix”
  • Red Hat Enterprise Linux AppStream (v. 9) haproxy 2.4.22-1.el9
    fixed: vendor fix RHSA-2023:6496
  • Red Hat Enterprise Linux 8 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

CISA SSVC

Exploitation
none
Automatable
yes
Technical impact
partial
Assessed
20 mo ago

Exploit prediction

1.20% chance of exploitation in the next 30 days, higher than 68% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
CISA ADP 3.1 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
NVD 3.1 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
CNA 3.1 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
OSV 3.1 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N

Affected packages

ecosystem package affected fixed in
bitnami haproxy
>=2.1.0, <2.1.1
>=2.2.0, <2.2.27
>=2.3.0, <2.3.1
>=2.4.0, <2.4.22
>=2.5.0, <2.5.12
>=2.6.0, <2.6.9
>=2.7.0, <2.7.1
2.1.1
2.2.27
2.3.1
2.4.22
2.5.12
2.6.9
2.7.1

Affected products

  • n/a HAProxy

Classification

Weakness
  • CWE-200 Exposure of Sensitive Information to an Unauthorized Actor
  • CWE-459 Incomplete Cleanup

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.