bcrypt-ruby has an Integer Overflow that Causes Zero Key-Strengthening Iterations at Cost=31 on JRuby
Résumé
bcrypt-ruby has an Integer Overflow that Causes Zero Key-Strengthening Iterations at Cost=31 on JRuby
Description d'origine
La description telle que publiée par la source (souvent en anglais).
bcrypt-ruby is a Ruby binding for the OpenBSD bcrypt() password hashing algorithm. Prior to version 3.1.22, an integer overflow in the Java BCrypt implementation for JRuby can cause zero iterations in the strengthening loop. Impacted applications must be setting the cost to 31 to see this happen. The JRuby implementation of bcrypt-ruby (BCrypt.java) computes the key-strengthening round count as a signed 32-bit integer. When cost=31 (the maximum allowed by the gem), signed integer overflow causes the round count to become negative, and the strengthening loop executes zero iterations. This collapses bcrypt from 2^31 rounds of exponential key-strengthening to effectively constant-time computation — only the initial EksBlowfish key setup and final 64x encryption phase remain. The resulting hash looks valid ($2a$31$...) and verifies correctly via checkpw, making the weakness invisible to the application. This issue is triggered only when cost=31 is used or when verifying a $2a$31$ hash. This problem has been fixed in version 3.1.22. As a workaround, set the cost to something less than 31.
Source: OSV.dev (Open Source Vulnerabilities) NVD GitHub Advisory OSV
État des correctifs par distribution
Paquets corrigés publiés par chaque distribution pour cette CVE
- Debian DEBIAN-CVE-2026-33306 ruby-bcrypt
Références
- advisory github.com
- advisory github.com
- advisory nvd.nist.gov
- patch github.com
- web github.com