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TI-2026-39884 Aliases CVE-2026-55204GHSA-4vj2-5mvx-3vcc

HAProxy - NULL Pointer Dereference in hpack_dht_insert Function

Priority MEDIUM 44CWE-476Published · Updated

Key facts

Attack vector
Network
Privileges required
None
User interaction
None
Attack complexity
Low
Attack requirements
None
Impact type
Denial of service
Confidentiality · integrity · availability
None · None · High
Fix status
Partial Red Hat: 24 fixed, 8 without a fix

Attack profile from CVSS 4.0 · CNA. Fix status from CNA and Red Hat. Impact type from CWE-476.

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.

Why it matters now

Exploitation None reported CISA SSVC · not in CISA KEV
EPSS 0.00484 41st percentileScored 2026-11-07
Fix Partial Red Hat: 21 advisoriesRed Hat: 24 fixed, 8 without a fix

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation
None
Automatable
Yes
Technical impact
Partial

The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.

Affected products

VendorProductAffected versionsFixed inStatusSource
HAProxyhaproxyup to 3.4.0—Patch availableCNA
  • haproxy VendorHAProxy Affected up to 3.4.0 Fixed in — Patch available CNA

CPE configurations NVD · 1

CPEVersionsRoleVendor
cpe:2.3:a:haproxy:haproxy:*:*:*:*:*:*:*:*before 2.4.36; 2.5 to before 2.6.30; 2.7 to before 2.8.25; 2.9 to before 3.0.24; 3.1 to before 3.2.20; 3.3 to before 3.4.1VulnerableHAProxy
  • cpe:2.3:a:haproxy:haproxy:*:*:*:*:*:*:*:* Versions before 2.4.36; 2.5 to before 2.6.30; 2.7 to before 2.8.25; 2.9 to before 3.0.24; 3.1 to before 3.2.20; 3.3 to before 3.4.1 Vulnerable ·HAProxy

Remediation

Red Hat 21 advisories

  • RHSA-2026:90274 Released 2026-10-27 · Red Hat rating Important
    OpenShift Container Platform 4.12.102 bug fix and security update
    • Red Hat OpenShift Container Platform 4.12 registry.redhat.io/openshift4/cloud-network-config-controller-rhel8, registry.redhat.io/openshift4/egress-router-cni-rhel8, registry.redhat.io/openshift4/kubevirt-csi-driver-rhel8 +47
  • RHSA-2026:89839 Released 2026-10-27 · Red Hat rating Important
    OpenShift Container Platform 4.14.77 bug fix and security update
    • Red Hat OpenShift Container Platform 4.14 registry.redhat.io/openshift4/cloud-network-config-controller-rhel8, registry.redhat.io/openshift4/egress-router-cni-rhel8, registry.redhat.io/openshift4/kubevirt-csi-driver-rhel8 +47
  • RHSA-2026:79039 Released 2026-10-15 · Red Hat rating Important
    OpenShift Container Platform 4.18.57 bug fix and security update
    • Red Hat OpenShift Container Platform 4.18 registry.redhat.io/openshift4/frr-rhel9, registry.redhat.io/openshift4/oc-mirror-plugin-rhel9, registry.redhat.io/openshift4/ose-agent-installer-node-agent-rhel9 +18
Show 18 more Red Hat advisories
  • RHSA-2026:77552 Released 2026-10-15 · Red Hat rating Important
    OpenShift Container Platform 4.17.59 bug fix and security update
    • Red Hat OpenShift Container Platform 4.17 registry.redhat.io/openshift4/frr-rhel9, registry.redhat.io/openshift4/ose-agent-installer-node-agent-rhel9, registry.redhat.io/openshift4/ose-baremetal-installer-rhel9 +12
  • RHSA-2026:77616 Released 2026-10-15 · Red Hat rating Important
    OpenShift Container Platform 4.16.73 bug fix and security update
    • Red Hat OpenShift Container Platform 4.16 registry.redhat.io/openshift4/ose-cluster-csi-snapshot-controller-rhel9-operator, registry.redhat.io/openshift4/ose-console-rhel9-operator, registry.redhat.io/openshift4/ose-haproxy-router-rhel9 +4
  • RHSA-2026:71447 Released 2026-09-30 · Red Hat rating Important
    OpenShift Container Platform 4.19.49 bug fix and security update
    • Red Hat OpenShift Container Platform 4.19 registry.redhat.io/openshift4/ose-agent-installer-node-agent-rhel9, registry.redhat.io/openshift4/ose-aws-ebs-csi-driver-rhel9-operator, registry.redhat.io/openshift4/ose-azure-disk-csi-driver-rhel9-operator +8
  • RHSA-2026:68541 Released 2026-09-22 · Red Hat rating Important
    OpenShift Container Platform 4.20.39 bug fix and security update
    • Red Hat OpenShift Container Platform 4.20 registry.redhat.io/openshift4/egress-router-cni-rhel9, registry.redhat.io/openshift4/ose-cluster-ingress-rhel9-operator, registry.redhat.io/openshift4/ose-csi-external-resizer-rhel9 +10
  • RHSA-2026:68546 Released 2026-09-22 · Red Hat rating Important
    OpenShift Container Platform 4.21.34 bug fix and security update
    • Red Hat OpenShift Container Platform 4.21 registry.redhat.io/openshift4/egress-router-cni-rhel9, registry.redhat.io/openshift4/ose-agent-installer-node-agent-rhel9, registry.redhat.io/openshift4/ose-aws-ebs-csi-driver-rhel9-operator +14
  • RHSA-2026:66358 Released 2026-09-15 · Red Hat rating Important
    OpenShift Container Platform 4.22.14 bug fix and security update
    • Red Hat OpenShift Container Platform 4.22 registry.redhat.io/openshift4/aws-karpenter-provider-aws-rhel9, registry.redhat.io/openshift4/aws-kms-encryption-provider-rhel9, registry.redhat.io/openshift4/aws-node-termination-handler-rhel9 +47
  • RHSA-2026:66018 Released 2026-09-09 · Red Hat rating Important
    Red Hat Update Infrastructure 5.3 security update
    • Red Hat Update Infrastructure 5 registry.redhat.io/rhui5/cds-kubernetes-rhel9, registry.redhat.io/rhui5/cds-rhel9, registry.redhat.io/rhui5/haproxy-rhel9 +2
  • RHSA-2026:55859 Released 2026-08-17 · Red Hat rating Important
    haproxy security update
    • Red Hat Enterprise Linux AppStream (v. 8) haproxy-1.8.27-5.el8_10.2
  • RHSA-2026:55860 Released 2026-08-17 · Red Hat rating Important
    haproxy security update
    • Red Hat Enterprise Linux AppStream E4S (v.8.8) haproxy-1.8.27-5.el8_8.2
    • Red Hat Enterprise Linux AppStream TUS (v.8.8) haproxy-1.8.27-5.el8_8.2
  • RHSA-2026:55862 Released 2026-08-17 · Red Hat rating Important
    haproxy security update
    • Red Hat Enterprise Linux AppStream AUS (v.8.6) haproxy-1.8.27-4.el8_6.2
    • Red Hat Enterprise Linux AppStream EUS EXTENSION (v.8.6) haproxy-1.8.27-4.el8_6.2
  • RHSA-2026:55861 Released 2026-08-17 · Red Hat rating Important
    haproxy security update
    • Red Hat Enterprise Linux AppStream AUS (v.8.4) haproxy-1.8.27-2.el8_4.2
    • Red Hat Enterprise Linux AppStream EUS EXTENSION (v.8.4) haproxy-1.8.27-2.el8_4.2
  • RHSA-2026:55803 Released 2026-08-17 · Red Hat rating Important
    haproxy security update
    • Red Hat Enterprise Linux AppStream EUS (v.9.6) haproxy-2.4.22-4.el9_6.3
  • RHSA-2026:55802 Released 2026-08-17 · Red Hat rating Important
    haproxy security update
    • Red Hat Enterprise Linux AppStream E4S (v.9.2) haproxy-2.4.17-6.el9_2.5
  • RHSA-2026:55801 Released 2026-08-17 · Red Hat rating Important
    haproxy security update
    • Red Hat Enterprise Linux AppStream E4S (v.9.4) haproxy-2.4.22-3.el9_4.3
  • RHSA-2026:55800 Released 2026-08-17 · Red Hat rating Important
    haproxy security update
    • Red Hat Enterprise Linux AppStream EUS (v. 10.0) haproxy-3.0.5-4.el10_0.3
  • RHSA-2026:55772 Released 2026-08-17 · Red Hat rating Important
    haproxy security update
    • Red Hat Enterprise Linux AppStream (v. 9) haproxy-2.8.14-3.el9_8.2
  • RHSA-2026:55679 Released 2026-08-17 · Red Hat rating Important
    haproxy security update
    • Red Hat Enterprise Linux AppStream (v. 10) haproxy-3.0.5-6.el10_2.2
  • RHSA-2026:35453 Released 2026-07-03 · Red Hat rating Important
    Red Hat Hardened Images RPMs bug fix and enhancement update
    • Red Hat Hardened Images haproxy-3.0.25-0.1.hum1@aarch64, haproxy-3.0.25-0.1.hum1@src, haproxy-3.0.25-0.1.hum1@x86_64

Vendor assessments

Red Hat

Red Hat rating: Important. Red Hat's page for this CVE →

ProductStatusPlan or fix
Red Hat Ceph Storage 5AffectedNo fix yet: Fix deferred
Red Hat Ceph Storage 6AffectedNo fix yet: Fix deferred
Red Hat Ceph Storage 7AffectedNo fix yet: Fix deferred
Red Hat Ceph Storage 8AffectedNo fix yet: Fix deferred
Red Hat Ceph Storage 9AffectedNo fix yet: Fix deferred
Red Hat Enterprise Linux 7AffectedNo fix planned: Out of support scope
Red Hat OpenShift Container Platform 4AffectedNo fix yet
Red Hat OpenShift Container Platform 5AffectedNo fix yet
Red Hat Enterprise Linux AppStream (v. 10)Fixed RHSA-2026:55679
Red Hat Enterprise Linux AppStream (v. 8)Fixed RHSA-2026:55859
Red Hat Enterprise Linux AppStream (v. 9)Fixed RHSA-2026:55772
Red Hat Enterprise Linux AppStream AUS (v.8.4)Fixed RHSA-2026:55861
Red Hat Enterprise Linux AppStream AUS (v.8.6)Fixed RHSA-2026:55862
Red Hat Enterprise Linux AppStream E4S (v.8.8)Fixed RHSA-2026:55860
Red Hat Enterprise Linux AppStream E4S (v.9.2)Fixed RHSA-2026:55802
Red Hat Enterprise Linux AppStream E4S (v.9.4)Fixed RHSA-2026:55801
Red Hat Enterprise Linux AppStream EUS (v. 10.0)Fixed RHSA-2026:55800
Red Hat Enterprise Linux AppStream EUS (v.9.6)Fixed RHSA-2026:55803
Red Hat Enterprise Linux AppStream EUS EXTENSION (v.8.4)Fixed RHSA-2026:55861
Red Hat Enterprise Linux AppStream EUS EXTENSION (v.8.6)Fixed RHSA-2026:55862
Red Hat Enterprise Linux AppStream TUS (v.8.8)Fixed RHSA-2026:55860
Red Hat Hardened ImagesFixed RHSA-2026:35453
Red Hat OpenShift Container Platform 4.12Fixed RHSA-2026:90274
Red Hat OpenShift Container Platform 4.14Fixed RHSA-2026:89839
Red Hat OpenShift Container Platform 4.16Fixed RHSA-2026:77616
Red Hat OpenShift Container Platform 4.17Fixed RHSA-2026:77552
Red Hat OpenShift Container Platform 4.18Fixed RHSA-2026:79039
Red Hat OpenShift Container Platform 4.19Fixed RHSA-2026:71447
Red Hat OpenShift Container Platform 4.20Fixed RHSA-2026:68541
Red Hat OpenShift Container Platform 4.21Fixed RHSA-2026:68546
Red Hat OpenShift Container Platform 4.22Fixed RHSA-2026:66358
Red Hat Update Infrastructure 5Fixed RHSA-2026:66018
Not affected: 12 products
  • Red Hat OpenShift Container Platform 4
  • Red Hat OpenShift Container Platform 4.12
  • Red Hat OpenShift Container Platform 4.14
  • Red Hat OpenShift Container Platform 4.16
  • Red Hat OpenShift Container Platform 4.17
  • Red Hat OpenShift Container Platform 4.18
  • Red Hat OpenShift Container Platform 4.19
  • Red Hat OpenShift Container Platform 4.20
  • Red Hat OpenShift Container Platform 4.21
  • Red Hat OpenShift Container Platform 4.22
  • Red Hat OpenShift Container Platform 5
  • Red Hat Update Infrastructure 5

Timeline

  1. 2026-10-02 Threatist record created from CVE-2026-55204
  2. 2026-10-03 Alias added: GHSA-4vj2-5mvx-3vcc
  3. 2026-10-16 Fix available: RHSA-2026:77616 · Red Hat
  4. 2026-10-16 Fix available: RHSA-2026:77552 · Red Hat
  5. 2026-10-16 Fix available: RHSA-2026:79039 · Red Hat
  6. 2026-10-16 Fix available: Red Hat OpenShift Container Platform 4.16, Red Hat OpenShift Container Platform 4.17, Red Hat OpenShift Container Platform 4.18 · Red Hat
  7. 2026-10-29 Fix available: Red Hat OpenShift Container Platform 4.12, Red Hat OpenShift Container Platform 4.14 · Red Hat
  8. 2026-10-30 Fix available: RHSA-2026:89839 · Red Hat
  9. 2026-10-30 Fix available: RHSA-2026:90274 · Red Hat
  10. 2026-10-30 Affected versions changed · Red Hat

References

Patch 1

  • TI-2020-08973 In hpack_dht_insert in hpack-tbl.c in the HPACK decoder in HAProxy 1.8 through 2.x before… CVSS 3.1HIGH 8.8
  • TI-2023-21094 HAProxy through 2.0.32, 2.1.x and 2.2.x through 2.2.30, 2.3.x and 2.4.x through 2.4.23… CVSS 3.1HIGH 7.2
  • TI-2019-10602 HAProxy through 2.0.2 allows attackers to cause a denial of service (ha_panic) via… CVSS 3.0HIGH 7.5
  • TI-2021-17418 An integer overflow exists in HAProxy 2.0 through 2.5 in htx_add_header that can be… CVSS 3.1HIGH 7.5
  • TI-2016-04651 HAproxy 1.6.x before 1.6.6, when a deny comes from a reqdeny rule, allows remote… CVSS 3.0HIGH 7.5
  • TI-2026-25946 An issue was discovered in HAProxy before 3.3.6. CVSS 3.1MEDIUM 5.8
See all 35 →

Sources

This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences