CVE-2026-56766

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Source
https://cve.org/CVERecord?id=CVE-2026-56766
Import Source
https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-56766.json
JSON Data
https://api.osv.dev/v1/vulns/CVE-2026-56766
Downstream
Related
Published
2026-06-25T18:01:07.362Z
Modified
2026-08-12T16:41:28.806281Z
Severity
  • 8.6 (High) CVSS_V4 - CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:A/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N CVSS Calculator
Summary
Hydra - Stack Buffer Overflow in NTLM Authentication Handler
Details

Hydra through 9.7, fixed in commit 9cc84c2, contains a stack buffer overflow in NTLM authentication across SMTP, POP3, IMAP, NNTP, HTTP, HTTP-Proxy, and HTTP-Proxy-Urlenum modules when processing malicious NTLM Type-2 challenges. A malicious server can send a crafted NTLM Type-2 challenge with an excessively long domain string, causing base64-encoded response data to overflow a 500-byte stack buffer by 18 to 330 bytes, enabling remote code execution on systems without stack protection.

Database specific 
{
    "cna_assigner": "VulnCheck",
    "cwe_ids": [
        "CWE-121"
    ],
    "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/56xxx/CVE-2026-56766.json"
}
References

Affected packages

Git / github.com/vanhauser-thc/thc-hydra

Affected ranges

Type
GIT
Repo
https://github.com/vanhauser-thc/thc-hydra
Events
Introduced
0 Unknown introduced commit / All previous commits are affected
Fixed
6c11ce2dff19ce81630c12b001d821dcd4d1567c
Fixed
9cc84c20e75f5fef6bb1790bb9ada2afad2204e2
Database specific
Show details 
{
    "extracted_events": [
        {
            "introduced": "0"
        },
        {
            "fixed": "9.7"
        }
    ],
    "source": [
        "DESCRIPTION",
        "REFERENCES"
    ]
}

Affected versions

8.*
8.3
8.6
v8.*
v8.2
v8.4
v8.5
v8.8
v8.9.1
v9.*
v9.0
v9.1
v9.2
v9.3
v9.4
v9.5
v9.6
v9.7

Database specific

source 
"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-56766.json"
vanir_signatures 
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    {
        "target": {
            "file": "hydra-imap.c"
        },
        "deprecated": false,
        "source": "https://github.com/vanhauser-thc/thc-hydra/commit/9cc84c20e75f5fef6bb1790bb9ada2afad2204e2",
        "id": "CVE-2026-56766-0c98c52c",
        "signature_version": "v1",
        "digest": {
            "threshold": 0.9,
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            ]
        },
        "signature_type": "Line"
    },
    {
        "target": {
            "file": "hydra-pop3.c"
        },
        "deprecated": false,
        "source": "https://github.com/vanhauser-thc/thc-hydra/commit/9cc84c20e75f5fef6bb1790bb9ada2afad2204e2",
        "id": "CVE-2026-56766-1305a1f9",
        "signature_version": "v1",
        "digest": {
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            ]
        },
        "signature_type": "Line"
    },
    {
        "target": {
            "file": "hydra-http.c"
        },
        "deprecated": false,
        "source": "https://github.com/vanhauser-thc/thc-hydra/commit/9cc84c20e75f5fef6bb1790bb9ada2afad2204e2",
        "id": "CVE-2026-56766-24ef6bb7",
        "signature_version": "v1",
        "digest": {
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        },
        "signature_type": "Line"
    },
    {
        "target": {
            "function": "start_pop3",
            "file": "hydra-pop3.c"
        },
        "deprecated": false,
        "source": "https://github.com/vanhauser-thc/thc-hydra/commit/9cc84c20e75f5fef6bb1790bb9ada2afad2204e2",
        "id": "CVE-2026-56766-27a70e75",
        "signature_version": "v1",
        "digest": {
            "length": 7538.0,
            "function_hash": "149535296753010222742306050121223423350"
        },
        "signature_type": "Function"
    },
    {
        "target": {
            "file": "hydra-smtp.c"
        },
        "deprecated": false,
        "source": "https://github.com/vanhauser-thc/thc-hydra/commit/9cc84c20e75f5fef6bb1790bb9ada2afad2204e2",
        "id": "CVE-2026-56766-311a4852",
        "signature_version": "v1",
        "digest": {
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            "line_hashes": [
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            ]
        },
        "signature_type": "Line"
    },
    {
        "target": {
            "function": "start_http_proxy_urlenum",
            "file": "hydra-http-proxy-urlenum.c"
        },
        "deprecated": false,
        "source": "https://github.com/vanhauser-thc/thc-hydra/commit/9cc84c20e75f5fef6bb1790bb9ada2afad2204e2",
        "id": "CVE-2026-56766-5b7f7a6e",
        "signature_version": "v1",
        "digest": {
            "length": 6627.0,
            "function_hash": "137960210208216958018972478822960075752"
        },
        "signature_type": "Function"
    },
    {
        "target": {
            "function": "start_smtp",
            "file": "hydra-smtp.c"
        },
        "deprecated": false,
        "source": "https://github.com/vanhauser-thc/thc-hydra/commit/9cc84c20e75f5fef6bb1790bb9ada2afad2204e2",
        "id": "CVE-2026-56766-5f34d4c9",
        "signature_version": "v1",
        "digest": {
            "length": 6056.0,
            "function_hash": "337775584107080223284065532835179464867"
        },
        "signature_type": "Function"
    },
    {
        "target": {
            "function": "start_nntp",
            "file": "hydra-nntp.c"
        },
        "deprecated": false,
        "source": "https://github.com/vanhauser-thc/thc-hydra/commit/9cc84c20e75f5fef6bb1790bb9ada2afad2204e2",
        "id": "CVE-2026-56766-7e7e4b04",
        "signature_version": "v1",
        "digest": {
            "length": 5983.0,
            "function_hash": "77233272943885351528390861051041917127"
        },
        "signature_type": "Function"
    },
    {
        "target": {
            "function": "start_http",
            "file": "hydra-http.c"
        },
        "deprecated": false,
        "source": "https://github.com/vanhauser-thc/thc-hydra/commit/9cc84c20e75f5fef6bb1790bb9ada2afad2204e2",
        "id": "CVE-2026-56766-8f77bc95",
        "signature_version": "v1",
        "digest": {
            "length": 8242.0,
            "function_hash": "146931814249048069120793061934488840833"
        },
        "signature_type": "Function"
    },
    {
        "target": {
            "file": "hydra-http-proxy.c"
        },
        "deprecated": false,
        "source": "https://github.com/vanhauser-thc/thc-hydra/commit/9cc84c20e75f5fef6bb1790bb9ada2afad2204e2",
        "id": "CVE-2026-56766-970b1f7f",
        "signature_version": "v1",
        "digest": {
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        },
        "signature_type": "Line"
    },
    {
        "target": {
            "function": "start_http_proxy",
            "file": "hydra-http-proxy.c"
        },
        "deprecated": false,
        "source": "https://github.com/vanhauser-thc/thc-hydra/commit/9cc84c20e75f5fef6bb1790bb9ada2afad2204e2",
        "id": "CVE-2026-56766-a3498009",
        "signature_version": "v1",
        "digest": {
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            "function_hash": "261533842065678094144150057478469060181"
        },
        "signature_type": "Function"
    },
    {
        "target": {
            "file": "hydra-http-proxy-urlenum.c"
        },
        "deprecated": false,
        "source": "https://github.com/vanhauser-thc/thc-hydra/commit/9cc84c20e75f5fef6bb1790bb9ada2afad2204e2",
        "id": "CVE-2026-56766-a7cc36ff",
        "signature_version": "v1",
        "digest": {
            "threshold": 0.9,
            "line_hashes": [
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        },
        "signature_type": "Line"
    },
    {
        "target": {
            "file": "hydra-nntp.c"
        },
        "deprecated": false,
        "source": "https://github.com/vanhauser-thc/thc-hydra/commit/9cc84c20e75f5fef6bb1790bb9ada2afad2204e2",
        "id": "CVE-2026-56766-c2ee553f",
        "signature_version": "v1",
        "digest": {
            "threshold": 0.9,
            "line_hashes": [
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        },
        "signature_type": "Line"
    },
    {
        "target": {
            "function": "start_imap",
            "file": "hydra-imap.c"
        },
        "deprecated": false,
        "source": "https://github.com/vanhauser-thc/thc-hydra/commit/9cc84c20e75f5fef6bb1790bb9ada2afad2204e2",
        "id": "CVE-2026-56766-c41666f5",
        "signature_version": "v1",
        "digest": {
            "length": 9551.0,
            "function_hash": "121957310138957187889185556097410338650"
        },
        "signature_type": "Function"
    }
]
vanir_signatures_modified 
"2026-08-12T16:41:28Z"