Vulnerability-Lookup

alsa-2026:55859

Vulnerability from osv_almalinux

Published

2026-08-17 00:00

Modified

2026-08-18 08:44

Summary

Important: haproxy security update

Details

The haproxy packages provide a reliable, high-performance network load balancer for TCP and HTTP-based applications.

Security Fix(es):

haproxy: HAProxy: Denial of Service via HPACK dynamic table insertions (CVE-2026-55204)

For more details about the security issue(s), including the impact, a CVSS score, acknowledgments, and other related information, refer to the CVE page(s) listed in the References section.

References

URL

Type

	https://access.redhat.com/errata/RHSA-2026:55859	ADVISORY
	https://access.redhat.com/security/cve/CVE-2026-55204	REPORT
	https://bugzilla.redhat.com/2490518	REPORT
	https://errata.almalinux.org/8/ALSA-2026-55859.html	ADVISORY

JSON

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{
  "affected": [
    {
      "package": {
        "ecosystem": "AlmaLinux:8",
        "name": "haproxy"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "1.8.27-5.el8_10.2"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "details": "The haproxy packages provide a reliable, high-performance network load balancer for TCP and HTTP-based applications.  \n\nSecurity Fix(es):  \n\n  * haproxy: HAProxy: Denial of Service via HPACK dynamic table insertions (CVE-2026-55204)\n\n\nFor more details about the security issue(s), including the impact, a CVSS score, acknowledgments, and other related information, refer to the CVE page(s) listed in the References section.\n",
  "id": "ALSA-2026:55859",
  "modified": "2026-08-18T08:44:27Z",
  "published": "2026-08-17T00:00:00Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://access.redhat.com/errata/RHSA-2026:55859"
    },
    {
      "type": "REPORT",
      "url": "https://access.redhat.com/security/cve/CVE-2026-55204"
    },
    {
      "type": "REPORT",
      "url": "https://bugzilla.redhat.com/2490518"
    },
    {
      "type": "ADVISORY",
      "url": "https://errata.almalinux.org/8/ALSA-2026-55859.html"
    }
  ],
  "related": [
    "CVE-2026-55204"
  ],
  "summary": "Important: haproxy security update"
}

CVE-2026-55204 (GCVE-0-2026-55204)

Vulnerability from cvelistv5 – Published: 2026-06-18 16:05 – Updated: 2026-07-14 21:33 X_Open Source

Title

HAProxy - NULL Pointer Dereference in hpack_dht_insert Function

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.

Severity

8.7 (High)


                        
                          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

7.5 (High)


                        
                          CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

SSVC

Exploitation: none Automatable: yes Technical Impact: partial

CISA Coordinator · CISA-ADP (v2.0.3)

Decision recorded 2026-06-18 17:26 UTC

CWE

CWE-476 - NULL Pointer Dereference

Assigner

VulnCheck mitre root

References

2 references

URL	Tags
https://github.com/haproxy/haproxy/commit/9a6d1fe…	patch
https://www.vulncheck.com/advisories/haproxy-null…	third-party-advisory

Impacted products

1 product

Vendor	Product	Version
haproxy	haproxy	Affected: 0 , ≤ 3.4.0 (semver) Unaffected: 9a6d1fe3f00d86ab4ea6ea6ea0a5d48fc058a513 (git) cpe:2.3:a:haproxy:aloha::::::::

Date Public

2026-06-16 00:00

Credits

Tristan Madani (@TristanInSec)

Show details on NVD website

JSON

To clipboard

{
  "containers": {
    "adp": [
      {
        "metrics": [
          {
            "other": {
              "content": {
                "id": "CVE-2026-55204",
                "options": [
                  {
                    "Exploitation": "none"
                  },
                  {
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                  },
                  {
                    "Technical Impact": "partial"
                  }
                ],
                "role": "CISA Coordinator",
                "timestamp": "2026-06-18T17:26:27.738915Z",
                "version": "2.0.3"
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        "providerMetadata": {
          "dateUpdated": "2026-06-18T17:26:38.498Z",
          "orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
          "shortName": "CISA-ADP"
        },
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    ],
    "cna": {
      "affected": [
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          "packageURL": "pkg:github/haproxy/haproxy",
          "product": "haproxy",
          "repo": "https://github.com/haproxy/haproxy",
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      "cpeApplicability": [
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        },
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          "url": "https://www.vulncheck.com/advisories/haproxy-null-pointer-dereference-in-hpack-dht-insert-function"
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    "datePublished": "2026-06-18T16:05:52.058Z",
    "dateReserved": "2026-06-16T15:53:37.765Z",
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  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}

Sightings

Author	Source	Type	Date	Other

Nomenclature

Seen: The vulnerability was mentioned, discussed, or observed by the user.
Confirmed: The vulnerability has been validated from an analyst's perspective.
Published Proof of Concept: A public proof of concept is available for this vulnerability.
Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
Not confirmed: The user expressed doubt about the validity of the vulnerability.
Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.

Detection rules are retrieved from Rulezet.

The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base model, served locally by ML-Gateway. They have not been verified by an analyst and are provided for guidance only.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.

Action not permitted

alsa-2026:55859

Vulnerability from osv_almalinux

CVE-2026-55204 (GCVE-0-2026-55204)

Tags

Sightings

Nomenclature