CVE-2026-43974

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Source

https://cve.org/CVERecord?id=CVE-2026-43974

Import Source

https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-43974.json

JSON Data

https://api.osv.dev/v1/vulns/CVE-2026-43974

Aliases

Published

2026-06-08T14:12:36Z

Modified

2026-08-20T03:54:18Z

Severity

8.7 (High) CVSS_V4 - 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 CVSS Calculator

Summary

gun HTTP/1.1 client accepts unsolicited 101 Switching Protocols response allowing server-driven protocol hijack and OOM

Details

Unexpected Status Code or Return Value vulnerability in ninenines gun (gun_http module) allows a malicious HTTP server to force the client into raw protocol mode via an unsolicited 101 Switching Protocols response.

In gun_http:handle_inform/8, when a 101 Switching Protocols response is received over HTTP/1.1, the function verifies only that the Upgrade header is syntactically valid and that the stream reference is a plain reference(). It does not check whether the client ever sent an Upgrade or Connection: upgrade header on the corresponding request. Because this check is absent, any 101 response (solicited or not) causes gun to dispatch a gun_upgrade message to the caller and transition the entire connection to raw protocol mode.

A malicious or compromised HTTP server can send an unsolicited 101 response to any HTTP/1.1 request, causing the gun client to abandon HTTP framing for that connection. Once in raw mode, gun_raw applies no flow control (flow=infinity) and re-arms socket active mode after every received packet, so the server can flood the client with arbitrary bytes. These are forwarded as unbounded gun_data messages to the owner process, exhausting its mailbox and BEAM memory, ultimately crashing the VM.

This issue affects gun: from 2.0.0 before 2.4.0.

Database specific

{
    "cna_assigner": "EEF",
    "cwe_ids": [
        "CWE-841"
    ],
    "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/43xxx/CVE-2026-43974.json",
    "unresolved_ranges": [
        {
            "extracted_events": [
                {
                    "introduced": "a3c2edbb8c807717e2f10520c6cf1e77a62eab2e"
                },
                {
                    "fixed": "5b48068c29ce5e112cb149b5857c7d4dc319a81b"
                }
            ],
            "source": "AFFECTED_FIELD"
        }
    ]
}

References

Affected packages

Git / github.com/ninenines/gun

Affected ranges

Type

GIT

Repo

https://github.com/ninenines/gun

Events

Introduced

33223e751267c5f249f3db1277c13904a1801b92

Fixed

8cc70ed78fc946e5d9c49e92d84bde64ca12db1f

Fixed

5b48068c29ce5e112cb149b5857c7d4dc319a81b

Database specific

Show details

{
    "cpe": "cpe:2.3:a:ninenines:gun:*:*:*:*:*:*:*:*",
    "extracted_events": [
        {
            "introduced": "2.0.0"
        },
        {
            "fixed": "2.4.0"
        }
    ],
    "source": [
        "CPE_RANGE",
        "REFERENCES"
    ]
}

Affected versions

2.*

2.0.0

2.0.1

2.1.0

2.2.0

2.3.0

Database specific

source

"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-43974.json"