# CVE-2024-8796: Insufficient Default OTP Shared Secret Length

> Insufficient TOTP secret length in Devise-Two-Factor allows attackers to more easily guess secrets and bypass two-factor authentication.

- **Severity:** Medium 6.0 (`CVSS:4.0/AV:N/AC:H/AT:P/PR:L/UI:N/VC:H/VI:N/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:** Yes
- **Published:** 17 Sep 2024
- **Updated:** 20 Sep 2024
- **Also known as:** DEBIAN-CVE-2024-8796, GHSA-qjxf-mc72-wjr2, UBUNTU-CVE-2024-8796

## What is CVE-2024-8796?

CVE-2024-8796 is a medium-severity vulnerability in devise-two-factor, published on 17 Sep 2024. Any signed-in user can exploit it over the network, with no action from the victim.

### Official description

Under the default configuration, Devise-Two-Factor versions >= 2.2.0 & < 6.0.0 generate TOTP shared secrets that are 120 bits instead of the 128-bit minimum defined by RFC 4226. Using a shared secret shorter than the minimum to generate a multi-factor authentication code could make it easier for an attacker to guess the shared secret and generate valid TOTP codes.

Weakness: CWE-331 (Insufficient Entropy)

## Which versions are affected by CVE-2024-8796?

4 open source packages ship an affected version, including devise-two-factor. It affects 1 product.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `devise-two-factor` | RubyGems | All versions | None |
| `devise-two-factor` | RubyGems | All versions | None |
| `devise-two-factor` | RubyGems | From 4.0.0 | 6.0.0 |
| `devise-two-factor` | RubyGems | From 4.0.0 | 6.0.0 |

Products: Tinfoilsecurity Devise-Two-Factor.

## How do I fix CVE-2024-8796?

Upgrade devise-two-factor to 6.0.0 or later.

## Is CVE-2024-8796 being exploited?

There is no known exploitation of CVE-2024-8796 in the wild and no public exploit code.

## Other vulnerabilities in devise-two-factor

- [CVE-2021-43177](https://insights.sbomify.com/CVE-2021-43177/): Improper one time password handling in devise-two-factor (medium 5.3)
- [CVE-2015-7225](https://insights.sbomify.com/CVE-2015-7225/): Tinfoil Devise-two-factor does not "burn" a successfully validated one-time password (OTP) (medium 5.3)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2024-8796 and fix it if it is affected.

What it is: CVE-2024-8796 is a medium-severity vulnerability in devise-two-factor, published on 17 Sep 2024. Any signed-in user can exploit it over the network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2024-8796 in the wild and no public exploit code.

Affected packages and fixed versions:
- devise-two-factor (RubyGems): affected all versions; no fix listed
- devise-two-factor (RubyGems): affected all versions; no fix listed
- devise-two-factor (RubyGems): affected from 4.0.0; fixed in 6.0.0
- devise-two-factor (RubyGems): affected from 4.0.0; fixed in 6.0.0

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-2024-8796/ (Markdown: https://insights.sbomify.com/CVE-2024-8796/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2024-8796
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2024-8796
- OSV: https://osv.dev/vulnerability/CVE-2024-8796

---
From sbomify Insights: https://insights.sbomify.com/CVE-2024-8796/
Summaries are generated and may contain mistakes; the official description above is the record.