CVE-2026-103651 MISP HOTP Token Replay via Stale Session-Cached Counter Allows Second-Factor Authentication Bypass
Attackers with valid sessions can replay consumed HOTP tokens to bypass second-factor authentication and access MISP accounts.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- None listed
What is CVE-2026-103651?
CVE-2026-103651 is a high-severity authentication bypass vulnerability in MISP, published on 1 Oct 2026. Any signed-in user can exploit it over the network, with no action from the victim.
Official description
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.
Which versions are affected by CVE-2026-103651?
How do I fix CVE-2026-103651?
No fix has been published for CVE-2026-103651 yet. Limit exposure of the affected software until one is available.
Upgrade, and rotate credentials and sessions that may have been exposed. More about Authentication bypass.
Is CVE-2026-103651 being exploited?
There is no known exploitation of CVE-2026-103651 in the wild and no public exploit code.
Sources
Also known as GHSA-28mq-63wc-4252.