CVE-2024-8796

Insufficient Default OTP Shared Secret Length

Published Sep 17, 2024 CVSS 4.0 · 6 Medium EPSS < 1% KEV · Not listed
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.

Remediation

Vendor Solution

Devise-Two-Factor should be upgraded to version v6.0.0 as soon as possible. After upgrading, the length of shared secrets and TOTP URLs generated by the library will increase since the new shared secrets will be longer. After upgrading or implementing the workaround, applications using Devise-Two-Factor may wish to migrate users to the new OTP length to provide increased protection for those accounts. Turning off OTP for users by setting otp_required_for_login to false is not recommended since it would leave accounts unprotected. However, you may wish to implement application logic that checks the length of a user's shared secret and prompts users to re-enroll in OTP.


Vendor Workaround

If upgrading is not possible, you can override the default otp_secret_length attribute in the model when configuring two_factor_authenticable and set it to a value of at least 26 to ensure newly generated shared secrets are at least 128-bits long.

Tracking

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Advisories

Source ID Title
EUVD EUVD EUVD-2024-2856 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.
Github GHSA Github GHSA GHSA-qjxf-mc72-wjr2 Devise-Two-Factor Authentication Uses Insufficient Default OTP Shared Secret Length
Ubuntu USN Ubuntu USN USN-7050-1 Devise-Two-Factor vulnerabilities
History
Type Values Removed Values Added
Metrics epss

{'score': 0.00129}

epss

{'score': 0.00144}

Type Values Removed Values Added
First Time appeared Tinfoilsecurity
Tinfoilsecurity devise-two-factor
CPEs cpe:2.3:a:tinfoilsecurity:devise-two-factor:*:*:*:*:*:*:*:*
cpe:2.3:a:tinfoilsecurity:devise-two-factor:1.0.0:*:*:*:*:*:*:*
Vendors & Products Tinfoilsecurity
Tinfoilsecurity devise-two-factor
Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'no', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}

Type Values Removed Values Added
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.
Title Insufficient Default OTP Shared Secret Length
Weaknesses CWE-331
References
Metrics cvssV3_1

{'score': 5.3, 'vector': 'CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:N/A:N'}

cvssV4_0

{'score': 6, 'vector': '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'}

Weaknesses

Sources

Status
PUBLISHED
Assigner
SNPS
Published
Updated
Sep 20, 2024, 7:43 PM
Reserved
Sep 13, 2024, 4:52 PM
Status
Analyzed
Published
Sep 17, 2024, 6:15 PM
Modified
Jun 17, 2026, 8:23 AM