CVE-2026-33306
bcrypt-ruby is a Ruby binding for the OpenBSD bcrypt() password hashing algorithm.
Published Mar 24, 2026 · corrected/updated Jun 17, 2026 · bcrypt-ruby project bcrypt-ruby · evidence confidence medium
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.
Grounded briefings
Catalog interpretations for three audiences. Each brief cites ingested metadata and the original advisories below. They are not independent research and they do not invent exploit steps.
Executive
CVE-2026-33306 is a medium public vulnerability record for bcrypt-ruby project bcrypt-ruby. It is not currently listed in the CISA Known Exploited catalog. Check the linked vendor or CERT advisories for patch status. This summary is a catalog interpretation of the ingested metadata and cites the original advisories below.
System administrator
Identify whether bcrypt-ruby project bcrypt-ruby is in your estate, then compare installed versions with the affected ranges. Affected packages or ranges on record: bcrypt-ruby project/bcrypt-ruby. Check the linked vendor or CERT advisories for patch status. Prefer the vendor or distribution advisory linked in Sources before changing production systems. This is a catalog interpretation, not a runbook.
Security analyst
Signals on file: CVSS 4.5. It is not currently listed in the CISA Known Exploited catalog. Weakness classes: CWE-190. Sources contributing to this record: cve_org, nvd. Public exploit references, when present, are outbound links only and are not proof of active exploitation. This is a catalog interpretation of stored metadata.
Exploitation and remediation
Exploitation evidence
Not listed as known exploited in CISA KEV. Not in CISA KEV or VulnCheck KEV.
Patch and remediation
No required-action text is stored yet. Use the vendor or CERT links in Sources for patch availability.
Safe detection guidance
Compare installed versions with the affected ranges below and verify the advisory from the original publisher. This site stores metadata and outbound links only; it does not ship exploit code or proof-of-concept payloads.
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