CVE-2026-85237
Undergoing Analysis Undergoing Analysis - In Progress

Brute Force Protection Bypass in MISP Email OTP

Publication date: 2026-09-03

Last updated on: 2026-09-03

Assigner: CIRCL

Description
A vulnerability in MISP's email-based one-time password (OTP) authentication flow allowed an attacker to perform an unrestricted number of OTP verification attempts. The email_otp() endpoint did not apply brute-force protection when validating submitted OTP values. An attacker who had reached the OTP verification stage, for example after successfully providing a user's primary authentication credentials, could repeatedly submit candidate OTP values while the same OTP remained valid. This significantly increased the feasibility of guessing the OTP and bypassing the additional authentication factor, potentially resulting in unauthorized access to the affected user's account. The issue was exacerbated by the fact that the OTP is associated with the user rather than with an individual pending login session, allowing multiple concurrent sessions to attempt guesses against the same valid OTP. The patch integrates the existing MISP brute-force protection mechanism into the email OTP flow. Failed OTP attempts are now counted against the user, further attempts are rejected once the configured threshold is reached, and the active OTP is invalidated when the attempt budget is exhausted. Blocklisted users are also prevented from requesting the generation of a fresh OTP. In addition, OTP comparison now uses hash_equals() and validates that the submitted value is a string.

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Meta Information

Published
2026-09-03
Last Modified
2026-09-03
Generated
2026-09-03
AI Q&A
2026-09-03
EPSS Evaluated
N/A
NVD
CVE-2026-85237
EUVD
EUVD-2026-70528

Affected Vendors & Products

Showing 2 associated CPEs
Vendor Product Version / Range
misp misp to 300 (inc)
misp misp to 5a6e4751-2f3f-4070-9419-94fb35b644e8 (inc)

Helpful Resources

Exploitability

CWE
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KEV
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CWE ID Description
CWE-307 The product does not implement sufficient measures to prevent multiple failed authentication attempts within a short time frame.

Attack-Flow Graph

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Executive Summary

This vulnerability is in MISP's email-based one-time password (OTP) authentication. It allows attackers to repeatedly guess OTP codes without any rate-limiting or brute-force protection. Since the OTP is tied to the user account rather than a specific login session, multiple attempts can be made against the same valid OTP, increasing the risk of unauthorized account access.

Detection Guidance

Monitor MISP logs for repeated failed OTP attempts from the same user or IP address. Check for multiple concurrent sessions attempting OTP verification against the same valid token. Use network traffic analysis to detect brute-force patterns targeting the email_otp() endpoint.

Impact Analysis

If exploited, this vulnerability could allow an attacker to bypass the additional authentication factor (OTP) and gain unauthorized access to your MISP account. This could lead to data breaches, unauthorized modifications, or misuse of sensitive information associated with your account.

Compliance Impact

This vulnerability could lead to unauthorized access to user accounts, potentially exposing sensitive personal or health data. For GDPR, this may violate principles of data protection by design and default, as well as security requirements under Article 32. For HIPAA, it could compromise the confidentiality of protected health information, violating the Security Rule's safeguards for access controls and integrity.

Mitigation Strategies

Apply the patch from the MISP commit 8658062ea which adds brute-force protection to the email OTP verification process. This includes rate-limiting failed attempts, using hash_equals() for secure OTP comparison, and invalidating OTPs after the attempt limit is reached.

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