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Fencer Vulns
high 7.5

CVE-2026-55204 json

HAProxy - NULL Pointer Dereference in hpack_dht_insert Function

published 2026-06-18 4 mo ago modified 2026-10-26 14 d ago also BIT-haproxy-2026-55204 , EUVD-2026-37906

cvss
7.5
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.5%
EPSS 0.5% chance of exploitation in 30 days, percentile 41%
public exploits
0
none known

Summary

HAProxy through 3.4.0, fixed in commit 9a6d1fe, contains a null pointer dereference vulnerability in hpack_dht_insert() within src/hpack-tbl.c that fails to validate the return value of hpack_dht_defrag() when the memory pool is exhausted. An attacker can trigger HPACK dynamic table insertions under memory pressure to dereference a NULL pointer and crash HAProxy worker processes, causing denial of service.

Patch / fix

  • bitnami haproxy 2.4.36, 2.6.30, 2.8.25, 3.0.24, 3.2.20, 3.4.1
  • haproxy haproxy 2.4.36, 2.6.30, 2.8.25, 3.0.24, 3.2.20, 3.4.1
  • haproxy Debian 14 3.2.20-1

debian advisories DEBIAN-CVE-2026-55204

  • haproxy Ubuntu 22.04 LTS 2.4.30-0ubuntu0.22.04.2
  • haproxy Ubuntu 24.04 LTS 2.8.16-0ubuntu0.24.04.3
  • haproxy Ubuntu 25.10 3.0.12-0ubuntu0.25.10.5
  • haproxy Ubuntu 26.04 LTS 3.2.9-1ubuntu2.2

ubuntu advisories UBUNTU-CVE-2026-55204

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 8 1.8.27-5.el8_10.2
  • haproxy RHEL 9 2.8.14-3.el9_8.2
  • haproxy RHEL 10.2 3.0.5-6.el10_2.2
  • haproxy hummingbird 1 3.0.25-0.1.hum1
  • haproxy RHEL 8.6 EUS_LONG_LIFE, RHEL 8.6 AUS 1.8.27-4.el8_6.2
  • haproxy RHEL 8.8 TUS, RHEL 8.8 E4S 1.8.27-5.el8_8.2
  • haproxy RHEL 8.4 EUS_LONG_LIFE, RHEL 8.4 AUS 1.8.27-2.el8_4.2
  • haproxy RHEL 9.6 EUS 2.4.22-4.el9_6.3

red hat advisories RHSA-2026:55862RHSA-2026:55859RHSA-2026:55860RHSA-2026:55861RHSA-2026:55803RHSA-2026:55801

  • haproxy SLE High Availability Extension 16.0, Linux Micro 6.2, SLES for SAP applications 16.0 3.2.21+git0.dbe43be37-160000.1.1
  • haproxy Linux Micro 6.0 2.8.11+git0.01c1056a4-4.1
  • haproxy Linux Micro 6.1 2.8.11+git0.01c1056a4-slfo.1.1_4.1
  • haproxy SLE High Availability Extension 15 SP7, SLE High Availability Extension 15 SP6 2.8.11+git0.01c1056a4-150600.3.15.1
  • haproxy SLE Micro 5.5, SLE Micro 5.4, SLE Micro 5.3 +2 more 2.4.22+git0.f8e3218e2-150400.3.28.1

suse advisories SUSE-SU-2026:22557-1SUSE-SU-2026:22544-1SUSE-SU-2026:22587-1SUSE-SU-2026:22515-1SUSE-SU-2026:22663-1SUSE-SU-2026:2652-1

  • haproxy openSUSE Leap 16.0 3.2.21+git0.dbe43be37-160000.1.1
  • haproxy openSUSE Tumbleweed 3.4.0+git31.fc300e9f2-1.1

opensuse advisories openSUSE-SU-2026:21245-1openSUSE-SU-2026:11090-1

  • haproxy AlmaLinux 10 3.0.5-6.el10_2.2
  • haproxy AlmaLinux 9 2.8.14-3.el9_8.2
  • haproxy AlmaLinux 8 1.8.27-5.el8_10.2

almalinux advisories ALSA-2026:55679ALSA-2026:55772ALSA-2026:55859

  • haproxy Rocky Linux 10 3.0.5-6.el10_2.2
  • haproxy Rocky Linux 9 2.8.14-3.el9_8.2
  • haproxy Rocky Linux 8 1.8.27-5.el8_10.2

rocky linux advisories RLSA-2026:55679RLSA-2026:55772RLSA-2026:55859

  • haproxy Azure Linux 3.0 2.9.11-7

azure linux advisories AZL-90261

Azure Linux vulnerability data, Copyright (c) Microsoft Corporation, from https://github.com/microsoft/AzureLinuxVulnerabilityData via OSV, under the MIT licence; changed: normalised to fixed package versions per release. MIT

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-2026-55204 updated cvss 7.5

haproxy: HAProxy: Denial of Service via HPACK dynamic table insertions

  • Red Hat Ceph Storage 5 rhceph/rhceph-haproxy-rhel8 Red Hat Ceph Storage 6 rhceph/rhceph-haproxy-rhel9 Red Hat Ceph Storage 7 rhceph/rhceph-haproxy-rhel9 Red Hat Ceph Storage 8 rhceph/rhceph-haproxy-rhel9 Red Hat Ceph Storage 9 rhceph-ci/haproxy, rhceph/rhceph-haproxy-rhel9, rhceph/rhceph-haproxy-rhel10
    affected: workaround, no fix available “Fix deferred”
  • Red Hat Enterprise Linux 7 haproxy
    affected: workaround, no fix planned “Out of support scope”
  • Red Hat OpenShift Container Platform 4 haproxy, haproxy18, haproxy20, haproxy22, haproxy26, haproxy28 Red Hat OpenShift Container Platform 5 haproxy, openshift5/ose-hypershift-rhel9, openshift5/ose-haproxy-router-rhel9
    affected: workaround, no fix available
  • Red Hat Enterprise Linux AppStream (v. 8) haproxy 1.8.27-5.el8_10.2
    fixed: vendor fix RHSA-2026:55859
  • Red Hat Enterprise Linux AppStream (v. 9) haproxy 2.8.14-3.el9_8.2
    fixed: vendor fix RHSA-2026:55772
  • Red Hat Enterprise Linux AppStream (v. 10) haproxy 3.0.5-6.el10_2.2
    fixed: vendor fix RHSA-2026:55679
  • Red Hat Enterprise Linux AppStream AUS (v.8.4) haproxy 1.8.27-2.el8_4.2
    fixed: vendor fix RHSA-2026:55861
  • Red Hat Enterprise Linux AppStream AUS (v.8.6) haproxy 1.8.27-4.el8_6.2
    fixed: vendor fix RHSA-2026:55862
show 21 more
  • Red Hat Enterprise Linux AppStream E4S (v.8.8) haproxy 1.8.27-5.el8_8.2
    fixed: vendor fix RHSA-2026:55860
  • Red Hat Enterprise Linux AppStream E4S (v.9.2) haproxy 2.4.17-6.el9_2.5
    fixed: vendor fix RHSA-2026:55802
  • Red Hat Enterprise Linux AppStream E4S (v.9.4) haproxy 2.4.22-3.el9_4.3
    fixed: vendor fix RHSA-2026:55801
  • Red Hat Enterprise Linux AppStream EUS (v. 10.0) haproxy 3.0.5-4.el10_0.3
    fixed: vendor fix RHSA-2026:55800
  • Red Hat Enterprise Linux AppStream EUS (v.9.6) haproxy 2.4.22-4.el9_6.3
    fixed: vendor fix RHSA-2026:55803
  • Red Hat Enterprise Linux AppStream EUS EXTENSION (v.8.4) haproxy 1.8.27-2.el8_4.2
    fixed: vendor fix RHSA-2026:55861
  • Red Hat Enterprise Linux AppStream EUS EXTENSION (v.8.6) haproxy 1.8.27-4.el8_6.2
    fixed: vendor fix RHSA-2026:55862
  • Red Hat Enterprise Linux AppStream TUS (v.8.8) haproxy 1.8.27-5.el8_8.2
    fixed: vendor fix RHSA-2026:55860
  • Red Hat Hardened Images haproxy 3.0.25-0.1.hum1
    fixed: vendor fix RHSA-2026:35453
  • Red Hat OpenShift Container Platform 4.12 openshift4/ose-haproxy-router 1792979370
    fixed: vendor fix RHSA-2026:90274
  • Red Hat OpenShift Container Platform 4.14 openshift4/ose-haproxy-router 1792891890
    fixed: vendor fix RHSA-2026:89839
  • Red Hat OpenShift Container Platform 4.16 openshift4/ose-haproxy-router-rhel9 1790856891
    fixed: vendor fix RHSA-2026:77616
  • Red Hat OpenShift Container Platform 4.17 openshift4/ose-haproxy-router-rhel9 1790855348
    fixed: vendor fix RHSA-2026:77552
  • Red Hat OpenShift Container Platform 4.18 openshift4/ose-haproxy-router-rhel9 1790854902
    fixed: vendor fix RHSA-2026:79039
  • Red Hat OpenShift Container Platform 4.19 openshift4/ose-haproxy-router-rhel9 1789920441
    fixed: vendor fix RHSA-2026:71447
  • Red Hat OpenShift Container Platform 4.20 openshift4/ose-haproxy-router-rhel9 1789471043
    fixed: vendor fix RHSA-2026:68541
  • Red Hat OpenShift Container Platform 4.21 openshift4/ose-haproxy-router-rhel9 1789379196
    fixed: vendor fix RHSA-2026:68546
  • Red Hat OpenShift Container Platform 4.22 openshift4/ose-haproxy-router-rhel9 1788888369
    fixed: vendor fix RHSA-2026:66358
  • Red Hat Update Infrastructure 5 rhui5/haproxy-rhel9 1788880456
    fixed: vendor fix RHSA-2026:66018
  • Red Hat OpenShift Container Platform 4 openshift4/ose-tests-rhel9, openshift4/ose-hypershift-rhel9, openshift4/ose-vsphere-cluster-api-controllers-rhel8
    not affected: vulnerable code not in execute path
  • Red Hat OpenShift Container Platform 4.12 openshift4/ose-cli 1792978815, openshift4/ose-pod 1792975145, openshift4/ose-etcd 1792974936, openshift4/ose-tests 1792891850, openshift4/ose-console 1792976642, openshift4/ose-coredns 1792977034, +183 more Red Hat OpenShift Container Platform 4.14 openshift4/ose-cli 1792888757, openshift4/ose-pod 1792892941, openshift4/ose-tests 1792894673, openshift4/ose-console 1792894610, openshift4/ose-coredns 1792892001, openshift4/ose-deployer 1792890904, +189 more Red Hat OpenShift Container Platform 4.16 openshift4/ose-cli-rhel9 1790855649, openshift4/ose-pod-rhel9 1790834845, openshift4/ose-sdn-rhel9 1790835944, openshift4/ose-etcd-rhel9 1790855884, openshift4/ose-tests-rhel9 1791346654, openshift4/ose-tools-rhel9 1791345252, +182 more Red Hat OpenShift Container Platform 4.17 openshift4/frr-rhel9 1790854263, openshift4/ose-cli-rhel9 1790854354, openshift4/ose-pod-rhel9 1790831180, openshift4/ose-etcd-rhel9 1790854609, openshift4/ose-tests-rhel9 1790856221, openshift4/ose-tools-rhel9 1790854392, +180 more Red Hat OpenShift Container Platform 4.18 openshift4/frr-rhel9 1790826545, openshift4/ose-cli-rhel9 1790882345, openshift4/ose-pod-rhel9 1790853956, openshift4/ose-etcd-rhel9 1791320060, openshift4/ose-tests-rhel9 1791373456, openshift4/ose-tools-rhel9 1791372072, +180 more Red Hat OpenShift Container Platform 4.19 openshift4/frr-rhel9 1789884391, openshift4/ose-cli-rhel9 1789896930, openshift4/ose-pod-rhel9 1789885260, openshift4/ose-etcd-rhel9 1789885218, openshift4/ose-tests-rhel9 1790074494, openshift4/ose-tools-rhel9 1790073159, +180 more
    +1 more products
    Red Hat OpenShift Container Platform 4.20 openshift4/frr-rhel9 1789467192, openshift4/ose-cli-rhel9 1789513935, openshift4/ose-pod-rhel9 1789474651, openshift4/ose-etcd-rhel9 1789467752, openshift4/ose-tests-rhel9 1789528745, openshift4/ose-tools-rhel9 1789527004, +182 more
    not affected: vulnerable code not present

4 more not affected in the full advisory

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
4 mo ago

Exploit prediction

0.48% chance of exploitation in the next 30 days, higher than 41% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
CNA 4.0 8.7 CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N
CNA 3.1 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
CNA 4.0 8.7 CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

Affected packages

ecosystem package affected fixed in
bitnami haproxy
<2.4.36
>=2.5.0, <2.6.30
>=2.7.0, <2.8.25
>=2.9.0, <3.0.24
>=3.1.0, <3.2.20
>=3.3.0, <3.4.1
2.4.36
2.6.30
2.8.25
3.0.24
3.2.20
3.4.1

Affected products

  • haproxy haproxy

Classification

Weakness

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.