CVE-2026-56766Public exploitNetwork attack vector

Remote code execution via oversized NTLM response

Published Jun 25, 2026 · Updated Jun 25, 2026

Stack buffer overflow in Hydra 9.7 and earlier allows remote attackers controlling an NTLM server to execute code during authentication. Across seven protocol modules, buildAuthResponse embeds a server-supplied domain in a Type-3 message before sprintf copies its Base64 form into a 500-byte stack buffer. The operator must direct Hydra to the malicious service, and code execution requires ineffective stack protection; protected builds terminate the process.

CVSS severity8.6
High
EPSS probability2.44%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Stack buffer overflow in Hydra 9.7 and earlier allows remote attackers controlling an NTLM server to execute code during authentication. Across seven protocol modules, buildAuthResponse embeds a server-supplied domain in a Type-3 message before sprintf copies its Base64 form into a 500-byte stack buffer. The operator must direct Hydra to the malicious service, and code execution requires ineffective stack protection; protected builds terminate the process.

The record

CVE
CVE-2026-56766
Published
Jun 25, 2026
Updated
Jun 25, 2026
Vendor
The Hacker's Choice
Product
Hydra
Classifications
CWE-121, T1203
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jun 25, 2026CVE publishedPublication date reported by the CVE source.
  2. Jun 25, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=0 <=9.7

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

The Hacker's Choice · Hydraversion=0 <=9.7

Published CVSS scores

8.8VulnCheckCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
8.6VulnCheckCVSS: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 describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-121Stack-based Buffer Overflow
T1203Exploitation for Client Execution

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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