CVE-2026-40586
Raw vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:NCVSS and EPSS are reproduced from their sources (NVD, FIRST EPSS). EPSS scores by FIRST (EPSS SIG), generated by Empirical Security. Risk Priority is our own derived reading, not an NVD score.
Summary
CVE-2026-40586 is a high-severity Improper Restriction of Excessive Authentication Attempts (CWE-307) vulnerability. Its CVSS base score is 7.5 (High).
Operationally, exploitation aligns with the MITRE ATT&CK technique Valid Accounts (T1078); ranked at the 41th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog.
The strongest mitigations our analysis identified map to AC-7 (Unsuccessful Logon Attempts) — see the control section below for these in your framework.
Deeper analysis AI-assisted summary
Synthesised by an AI model from the NVD description and linked references — a reading aid, not an authoritative source.
CVE-2026-40586 is a vulnerability in the login form handler of blueprintUE, a self-hosted tool for Unreal Engine developers, affecting versions prior to 4.2.0. The handler lacks any form of throttling, including IP-based rate limiting, per-account attempt counters, temporary lockouts, progressive delays, or CAPTCHA challenges, allowing failed authentication attempts to be processed at full network speed. This improper restriction of excessive authentication attempts (CWE-307) has a CVSS v3.1 base score of 7.5 (AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N), indicating high confidentiality impact potential from network-based exploitation without privileges or user interaction.
Any unauthenticated attacker with network access to the blueprintUE instance can exploit this vulnerability by submitting an unlimited number of credential guesses. This enables brute-force attacks, dictionary attacks, credential stuffing using data from breached databases, or targeted guesses against users with predictable passwords, despite the enforced password policy requiring 10+ characters with mixed case, digits, and special characters. Successful exploitation could grant unauthorized access to the tool's administrative functions or user accounts.
The GitHub security advisory (GHSA-m6c2-6p3h-8jv2) for the blueprintue-self-hosted-edition repository confirms the issue and states that it is fixed in version 4.2.0. Security practitioners should upgrade to 4.2.0 or later and consider implementing additional server-side protections like web application firewalls with rate limiting rules as interim mitigations.
OWASP Top 10 for Web (2025)
EU & UK References
- 🇪🇺 ENISA EUVD: EUVD-2026-24182
Vulnerability Data
blueprintUE is a tool to help Unreal Engine developers. Prior to 4.2.0, the login form handler performs no throttling of any kind. Failed authentication attempts are processed at full network speed with no IP-based rate limiting, no per-account attempt counter,…
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no temporary lockout, no progressive delay (Tarpit), and no CAPTCHA challenge. An attacker can submit an unlimited number of credential guesses. The password policy (10+ characters, mixed case, digit, special character) reduces the effective keyspace but does not prevent dictionary attacks, credential stuffing from breached databases, or targeted attacks against known users with predictable passwords. This vulnerability is fixed in 4.2.0.
- CWE(s)
Related Threats
MITRE ATT&CK Enterprise Techniques
CVEs Like This One
Affected Assets
Mitigating Controls
Control response
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- 2 hardening rules · 1 OS baseline
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Mitigating Controls (NIST 800-53 r5) AI
AC-7 directly enforces limits on consecutive failed logons, structurally blocking brute-force exploitation of the weakness.
Mitigating Controls (NIST CSF 2.0) AI
Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→CSF cross-walk (authority under review) — links open the control.
Authentication enforcement directly includes lockout, throttling, and MFA policies that prevent brute-force attempts.
Behavioral monitoring of authentication activity can detect excessive failed attempts after they occur.
Generating auth logs enables later detection or forensics but does not itself restrict attempts.
Mitigating Controls (ISO/IEC 27001:2022 Annex A) AI
Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→ISO cross-walk (authority under review) — links open the control.
A.8.5 directly mandates protection against brute force log-on attempts, so implementing it removes the absence of such restrictions that constitutes CWE-307.
Hardening callouts derived
Configuration rules from DISA STIG baselines that bear on weaknesses of the type cited by this CVE. Each rule is shown with the relationship its mapping actually records, against the CWE it was authored against. Derived via CVE→CWE over `controls_xwalks` (higher-evidence rows only; rows rated `none` are excluded).
RHEL 7 (2 rules)
- V-204427 The Red Hat Enterprise Linux operating system must be configured to lock accounts for a minimum of 15 minutes after three unsuccessful logon attempts within a 15-minute timeframe. blocks CWE-307
- V-204428 The Red Hat Enterprise Linux operating system must lock the associated account after three unsuccessful root logon attempts are made within a 15-minute period. blocks CWE-307