MISP HOTP Token Replay via Stale Session-Cached Counter Allows Second-Factor Authentication Bypass

Summary

MISP contains a vulnerability in its one-time password (OTP) authentication flow that allows replay of a consumed HOTP (paper) token and rewinding of the token counter. The HOTP verification logic compared the submitted token against a counter value that was cached in the user's session at the time the password was entered, rather than against the authoritative counter stored in the database. Because the session-cached counter is not updated after a token is successfully consumed, an attacker who holds a valid session (password already submitted) can reuse a previously burned HOTP token. The stale cached counter still matches the replayed token, granting a second successful authentication and effectively rewinding the counter state. Preconditions: • The target user has HOTP (paper token) second-factor authentication enabled. • The attacker possesses a valid session in which the password step has already been completed (the OTP step is pending). • The attacker has access to at least one HOTP token value (e.g., a paper token list). Security impact: • Bypass of the second authentication factor, allowing unauthorized access to a user's MISP account. • Corruption of the HOTP counter state, potentially invalidating subsequent legitimate tokens or enabling further replays. Affected versions: <2.5.48.

Timeline

1. Oct 1, 2026, 7:34 AM UTCCVE published
2. Oct 1, 2026, 3:31 PM UTCCISA SSVC assessment

   Exploitation: none · Automatable: no · Technical impact: total

3. Oct 1, 2026, 3:32 PM UTCRecord last updated

Affected versions

• MISP MISP

  fixed in 2.5.48

References 1