Vulnerable Library - bcrypt-3.1.11.gem
bcrypt() is a sophisticated and secure hash algorithm designed by The OpenBSD project
for hashing passwords. The bcrypt Ruby gem provides a simple wrapper for safely handling
passwords.
Library home page: https://rubygems.org/gems/bcrypt-3.1.11.gem
Sample Path to Dependency File: /Gemfile.lock
Path to vulnerable library: /tmp/containerbase/cache/.ruby/cache/bcrypt-3.1.11.gem
Found in HEAD commit: ab21a9f862ff3da3db0787ca394d129f490c3cfe
Vulnerabilities
| Vulnerability |
Severity |
 CVSS |
Exploit Maturity |
EPSS |
Dependency |
Type |
Fixed in (bcrypt version) |
Remediation Possible** |
Reachability |
| CVE-2026-33306 |
 Medium |
6.7 |
Not Defined |
0.228% |
bcrypt-3.1.11.gem |
Direct |
bcrypt - 3.1.22 |
❌ |
|
**In some cases, Remediation PR cannot be created automatically for a vulnerability despite the availability of remediation
Details
CVE-2026-33306
Vulnerable Library - bcrypt-3.1.11.gem
bcrypt() is a sophisticated and secure hash algorithm designed by The OpenBSD project
for hashing passwords. The bcrypt Ruby gem provides a simple wrapper for safely handling
passwords.
Library home page: https://rubygems.org/gems/bcrypt-3.1.11.gem
Sample Path to Dependency File: /Gemfile.lock
Path to vulnerable library: /tmp/containerbase/cache/.ruby/cache/bcrypt-3.1.11.gem
Dependency Hierarchy:
- ❌ bcrypt-3.1.11.gem (Vulnerable Library)
Found in HEAD commit: ab21a9f862ff3da3db0787ca394d129f490c3cfe
Found in base branch: main
Vulnerability Details
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.
Mend Note: The description of this vulnerability differs from MITRE.
Publish Date: 2026-03-24
URL: CVE-2026-33306
Threat Assessment
Exploit Maturity: Not Defined
EPSS: 0.228%
CVSS 3 Score Details (6.7)
Base Score Metrics:
- Exploitability Metrics:
- Attack Vector: Local
- Attack Complexity: High
- Privileges Required: None
- User Interaction: None
- Scope: Unchanged
- Impact Metrics:
- Confidentiality Impact: High
- Integrity Impact: High
- Availability Impact: None
For more information on CVSS3 Scores, click here.
Suggested Fix
Type: Upgrade version
Origin: GHSA-f27w-vcwj-c954
Release Date: 2026-03-19
Fix Resolution: bcrypt - 3.1.22
bcrypt() is a sophisticated and secure hash algorithm designed by The OpenBSD project for hashing passwords. The bcrypt Ruby gem provides a simple wrapper for safely handling passwords.
Library home page: https://rubygems.org/gems/bcrypt-3.1.11.gem
Sample Path to Dependency File: /Gemfile.lock
Path to vulnerable library: /tmp/containerbase/cache/.ruby/cache/bcrypt-3.1.11.gem
Found in HEAD commit: ab21a9f862ff3da3db0787ca394d129f490c3cfe
Vulnerabilities
**In some cases, Remediation PR cannot be created automatically for a vulnerability despite the availability of remediation
Details
Vulnerable Library - bcrypt-3.1.11.gem
bcrypt() is a sophisticated and secure hash algorithm designed by The OpenBSD project for hashing passwords. The bcrypt Ruby gem provides a simple wrapper for safely handling passwords.
Library home page: https://rubygems.org/gems/bcrypt-3.1.11.gem
Sample Path to Dependency File: /Gemfile.lock
Path to vulnerable library: /tmp/containerbase/cache/.ruby/cache/bcrypt-3.1.11.gem
Dependency Hierarchy:
Found in HEAD commit: ab21a9f862ff3da3db0787ca394d129f490c3cfe
Found in base branch: main
Vulnerability Details
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.
Mend Note: The description of this vulnerability differs from MITRE.
Publish Date: 2026-03-24
URL: CVE-2026-33306
Threat Assessment
Exploit Maturity: Not Defined
EPSS: 0.228%
CVSS 3 Score Details (6.7)
Base Score Metrics:
- Exploitability Metrics:
- Attack Vector: Local
- Attack Complexity: High
- Privileges Required: None
- User Interaction: None
- Scope: Unchanged
- Impact Metrics:
- Confidentiality Impact: High
- Integrity Impact: High
- Availability Impact: None
For more information on CVSS3 Scores, click here.Suggested Fix
Type: Upgrade version
Origin: GHSA-f27w-vcwj-c954
Release Date: 2026-03-19
Fix Resolution: bcrypt - 3.1.22