CVE-2026-33306
bcrypt-ruby is a Ruby binding for the OpenBSD bcrypt() password hashing algorithm.
Published Mar 24, 2026 · updated Jun 17, 2026 · bcrypt-ruby project bcrypt-ruby
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 ( ) computes the key-strengthening round count as a signed 32-bit integer. When (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 ( ) and verifies correctly via , making the weakness invisible to the application. This issue is triggered only when cost=31 is used or when verifying a hash. This problem has been fixed in version 3.1.22. As a workaround, set the cost to something less than 31.
Code
The project this record applies to. Exploit listings stay in References.
Timeline
Detection, updates, and resolution for this record.
Mar 24, 2026 · NIST NVD
Detected
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 ( ) computes the key-strengthening round count as a signed 32-
Jun 17, 2026 · NIST NVD
Updated
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 ( ) computes the key-strengthening round count as a signed 32-
Affected
- cpe bcrypt-ruby project/bcrypt-rubyversion unspecified
Sources
- CVE.orgVulnerability recordCVE-2026-33306
Official CVE identifier
cve.org - NIST NVDVulnerability recordCVE-2026-33306
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 t
nvd.nist.gov