CVE-2026-19773

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Source
https://cve.org/CVERecord?id=CVE-2026-19773
Import Source
https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-19773.json
JSON Data
https://api.osv.dev/v1/vulns/CVE-2026-19773
Downstream
Published
2026-09-15T18:01:09Z
Modified
2026-09-17T08:08:33Z
Severity
  • 9.8 (Critical) CVSS_V3 - CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H CVSS Calculator
Summary
libwebsockets HTTP/2 HPACK Path Header Parsing Out-Of-Bounds Write Remote Code Execution Vulnerability
Details

libwebsockets HTTP/2 HPACK Path Header Parsing Out-Of-Bounds Write Remote Code Execution Vulnerability. This vulnerability allows remote attackers to execute arbitrary code on affected installations of libwebsockets. Authentication is not required to exploit this vulnerability.

The specific flaw exists within the parsing of HTTP/2 HPACK path header. The issue results from the lack of proper validation of user-supplied data, which can result in a write past the end of an allocated buffer. An attacker can leverage this vulnerability to execute code in the context of the current process. Was ZDI-CAN-31036.

Database specific 
{
    "cna_assigner": "zdi",
    "cwe_ids": [
        "CWE-787"
    ],
    "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/19xxx/CVE-2026-19773.json",
    "unresolved_ranges": [
        {
            "extracted_events": [
                {
                    "introduced": "b4b5aed3903eaff09cd76a410f69bbe5dff66f8e"
                },
                {
                    "last_affected": "b4b5aed3903eaff09cd76a410f69bbe5dff66f8e"
                }
            ],
            "source": "AFFECTED_FIELD"
        }
    ]
}
References

Affected packages

Git / github.com/warmcat/libwebsockets

Affected ranges

Type
GIT
Repo
https://github.com/warmcat/libwebsockets
Events
Introduced
0 Unknown introduced commit / All previous commits are affected
Fixed
824151862f37bc72f46d9a3e01d5b9408d313a0b
Database specific
Show details 
{
    "source": "REFERENCES"
}

Affected versions

Other
deflate-stream-support
master-test-2015-11-06-1
master-test-2015-11-19-1
support-chrome-20-firefox-12
support-protocol-v7
support-protocol-v8-chrome-15-firefox-6
valgrind-clean
release-0.*
release-0.1
release-0.2
release-0.3
release-0.4
release-0.5
release-0.6
v1.*
v1.0-chrome25-firefox17
v1.1-chrome26-firefox18
v1.2-chrome26-firefox18
v1.21-chrome26-firefox18
v1.22-chrome26-firefox18
v1.23-chrome32-firefox24
v1.3-chrome37-firefox30
v1.4-chrome43-firefox-36
v1.5-chrome47-firefox41
v1.6.0-chrome48-firefox42
v1.7.0
v2.*
v2.0.0
v2.1-pre3
v2.1.0
v2.2.0
v2.3.0
v2.4.0
v3.*
v3.0.0
v3.1.0
v4.*
v4.0.0
v4.1.0
v4.2-rc1
v4.2.0
v4.3.0
v4.4.0
v4.5.0

Database specific

source 
"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-19773.json"
vanir_signatures 
[
    {
        "deprecated": false,
        "digest": {
            "line_hashes": [
                "272076028274921666560769073762661966029",
                "289674001653508133457875561273963551729",
                "211806482779604396098642240786168379754"
            ],
            "threshold": 0.9
        },
        "id": "CVE-2026-19773-639e663f",
        "signature_type": "Line",
        "signature_version": "v1",
        "source": "https://github.com/warmcat/libwebsockets/commit/824151862f37bc72f46d9a3e01d5b9408d313a0b",
        "target": {
            "file": "lib/roles/h2/hpack.c"
        }
    },
    {
        "deprecated": false,
        "digest": {
            "function_hash": "249488117909369390949700074553219546391",
            "length": 280
        },
        "id": "CVE-2026-19773-da13717f",
        "signature_type": "Function",
        "signature_version": "v1",
        "source": "https://github.com/warmcat/libwebsockets/commit/824151862f37bc72f46d9a3e01d5b9408d313a0b",
        "target": {
            "file": "lib/roles/h2/hpack.c",
            "function": "lws_frag_append"
        }
    }
]
vanir_signatures_modified 
"2026-09-17T08:08:33Z"