CVE-2026-33306: bcrypt-ruby is a Ruby binding for the OpenBSD bcrypt() password hashing algorithm

Q: How do I fix CVE-2026-33306?

bcrypt-ruby: upgrade to 3.1.22. Exact commands for each OS are on this page.

Q: Is CVE-2026-33306 being exploited?

CVE-2026-33306 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

Q: What does CVE-2026-33306 affect?

CVE-2026-33306 affects bcrypt-ruby. Severity is high (CVSS 7.5). 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 appli

Q: How urgent is CVE-2026-33306?

Priority 35/100. High severity; Remotely exploitable, no login, no user action

Routine

HIGH 7.5REMOTEUPGRADE

CVE-2026-33306 is a high-severity flaw (CVSS 7.5) affecting bcrypt-ruby. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

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 maxi

Why this priority

High severity
Remotely exploitable, no login, no user action

A fixed release or distro patch exists.

Risk facts

CVSS score	7.5 (High)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	0.2% (top 85%)
CISA exploited list	No
Weakness	CWE-190
Published	2026-03-24
Last modified	2026-06-17

Publisher (CNA): GitHub, Inc. · Vendor: bcrypt-ruby project

Last updated 2026-06-17 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-03-24 01:17 UTCPublished CVE record published
2026-06-17 10:37 UTCUpdated Record last modified

bcrypt-ruby project bcrypt-ruby UPGRADE

Affected: < 3.1.22

Fixed in: 3.1.22

Safe to downgrade to: no unaffected older release

1. Check installed version

apt-cache policy bcrypt-ruby || rpm -q bcrypt-ruby || bcrypt-ruby --version

2. UPGRADE to 3.1.22 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade bcrypt-ruby

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade bcrypt-ruby

Note

Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2026-33306?

bcrypt-ruby: upgrade to 3.1.22. Exact commands for each OS are on this page.

Is CVE-2026-33306 being exploited?

CVE-2026-33306 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2026-33306 affect?

CVE-2026-33306 affects bcrypt-ruby. Severity is high (CVSS 7.5). 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 appli

How urgent is CVE-2026-33306?

Priority 35/100. High severity; Remotely exploitable, no login, no user action

Software pages

Java vulnerabilities · Ruby vulnerabilities

References

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