# 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.

- **Severity:** High 7.6 (`CVSS:4.0/AV:N/AC:H/AT:N/PR:L/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 1 Oct 2026
- **Updated:** 1 Oct 2026
- **Also known as:** GHSA-28mq-63wc-4252

## 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.

Weakness: CWE-362 (Concurrent Execution using Shared Resource with Improper Synchronization), CWE-287 (Improper Authentication)

## 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.

## Is CVE-2026-103651 being exploited?

There is no known exploitation of CVE-2026-103651 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-103651 and fix it if it is affected.

What it is: 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.
Exploitation: There is no known exploitation of CVE-2026-103651 in the wild and no public exploit code.

Affected product: MISP. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-103651/ (Markdown: https://insights.sbomify.com/CVE-2026-103651/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-103651
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-103651
- OSV: https://osv.dev/vulnerability/CVE-2026-103651

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-103651/
Summaries are generated and may contain mistakes; the official description above is the record.