CVE-2026-55203

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Source
https://cve.org/CVERecord?id=CVE-2026-55203
Import Source
https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-55203.json
JSON Data
https://api.osv.dev/v1/vulns/CVE-2026-55203
Aliases
Downstream
ALSA (2)
AZL (1)
CGA (14)
CLSA (2)
DEBIAN (1)
MGASA (1)
MINI (8)
OESA (1)
openSUSE (2)
RHSA (7)
RLSA (2)
SUSE (7)
UBUNTU (1)
Related
ALSA (2)
openSUSE (2)
SUSE (7)
Published
2026-06-18T16:05:20Z
Modified
2026-11-04T07:22:45Z
Severity
  • 9.0 (Critical) CVSS_V4 - CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:H/VA:N/SC:L/SI:H/SA:N CVSS Calculator
Summary
HAProxy - Integer Overflow in FCGI Demux Record Length Field
Details

HAProxy through 3.4.0, fixed in commit 5985276, contains an integer overflow vulnerability in the fcgi_conn structure's drl field that allows buffer misparse as new FCGI record headers. When contentLength is 65535 and paddingLength is 1 or more, the drl field wraps to 0, causing incorrect record consumption and allowing malicious FastCGI backends to desynchronize the FCGI framing parser, potentially causing request routing errors, response smuggling, or memory safety issues.

Database specific 
{
    "cna_assigner": "VulnCheck",
    "cwe_ids": [
        "CWE-190"
    ],
    "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/55xxx/CVE-2026-55203.json"
}
References

Affected packages

Git / github.com/haproxy/haproxy

Affected ranges

Type
GIT
Repo
https://github.com/haproxy/haproxy
Events
Introduced
7832fb21fe2dd11ce44e996d8e86802731b871b2
Fixed
aed953088ebfdf6046e4a8d362f97d391c5793b4
Fixed
5985276735777634d8c85f1d73bb7764aab0d6dd
Database specific
Show details 
{
    "extracted_events": [
        {
            "cpe": "cpe:2.3:a:haproxy:haproxy:*:*:*:*:*:*:*:*",
            "range": [
                {
                    "introduced": "3.3"
                },
                {
                    "fixed": "3.4.1"
                }
            ],
            "source": "CPE_RANGE"
        },
        {
            "range": [
                {
                    "fixed": "5985276735777634d8c85f1d73bb7764aab0d6dd"
                }
            ],
            "source": "REFERENCES_COMMIT"
        }
    ]
}

Affected versions

v3.*
v3.3.0
v3.4-dev0

Database specific

source 
"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-55203.json"
vanir_signatures 
[
    {
        "deprecated": false,
        "digest": {
            "line_hashes": [
                "96977972760350919949608749764941568400",
                "279486608961056297162498042069419015337",
                "329278527771316655991926612995450268630",
                "303965689733421752164327482840650665067"
            ],
            "threshold": 0.9
        },
        "id": "CVE-2026-55203-e65cffc5",
        "signature_type": "Line",
        "signature_version": "v1",
        "source": "https://github.com/haproxy/haproxy/commit/5985276735777634d8c85f1d73bb7764aab0d6dd",
        "target": {
            "file": "src/mux_fcgi.c"
        }
    }
]
vanir_signatures_modified 
"2026-11-04T07:22:45Z"