DEBIAN-CVE-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 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.
DEBIAN-CVE-2026-33306
Primary source · Revision 1
Imported from structured advisory data. Source references identify upstream records or fields; verify affected versions and your deployed configuration.
Security context
Source reference: osv:DEBIAN-CVE-2026-33306
ruby-bcrypt
Source reference: /affected/0/package/name
- Affected versions
- 3.1.18-1
Source reference:
/affected/0/versions3.1.20-1Source reference:
/affected/0/versions3.1.21-1Source reference:
/affected/0/versions3.1.22-1Source reference:
/affected/0/versions - Fixed versions
- Not stated in this record
- Prerequisites
- Not stated in this record
ruby-bcrypt
Source reference: /affected/1/package/name
- Affected versions
- 3.1.20-1
Source reference:
/affected/1/versions3.1.21-1Source reference:
/affected/1/versions3.1.22-1Source reference:
/affected/1/versions - Fixed versions
- Not stated in this record
- Prerequisites
- Not stated in this record
ruby-bcrypt
Source reference: /affected/2/package/name
- Affected versions
- 3.1.20-1
Source reference:
/affected/2/versions3.1.21-1Source reference:
/affected/2/versions - Fixed versions
- 3.1.22-1
Source reference:
/affected/2/ranges - Prerequisites
- Not stated in this record
Structured affected-version data
Original package identities and version rules from this source.
[
{
"ranges": [
{
"type": "ECOSYSTEM",
"events": [
{
"introduced": "0"
}
]
}
],
"package": {
"name": "ruby-bcrypt",
"purl": "pkg:deb/debian/ruby-bcrypt?arch=source&distro=bookworm",
"ecosystem": "Debian:12"
},
"versions": [
"3.1.18-1",
"3.1.20-1",
"3.1.21-1",
"3.1.22-1"
],
"database_specific": {
"source": "https://storage.googleapis.com/debian-osv/debian-cve-osv/DEBIAN-CVE-2026-33306.json"
},
"ecosystem_specific": {
"urgency": "not yet assigned"
}
},
{
"ranges": [
{
"type": "ECOSYSTEM",
"events": [
{
"introduced": "0"
}
]
}
],
"package": {
"name": "ruby-bcrypt",
"purl": "pkg:deb/debian/ruby-bcrypt?arch=source&distro=trixie",
"ecosystem": "Debian:13"
},
"versions": [
"3.1.20-1",
"3.1.21-1",
"3.1.22-1"
],
"database_specific": {
"source": "https://storage.googleapis.com/debian-osv/debian-cve-osv/DEBIAN-CVE-2026-33306.json"
},
"ecosystem_specific": {
"urgency": "not yet assigned"
}
},
{
"ranges": [
{
"type": "ECOSYSTEM",
"events": [
{
"introduced": "0"
},
{
"fixed": "3.1.22-1"
}
]
}
],
"package": {
"name": "ruby-bcrypt",
"purl": "pkg:deb/debian/ruby-bcrypt?arch=source&distro=forky",
"ecosystem": "Debian:14"
},
"versions": [
"3.1.20-1",
"3.1.21-1"
],
"database_specific": {
"source": "https://storage.googleapis.com/debian-osv/debian-cve-osv/DEBIAN-CVE-2026-33306.json"
},
"ecosystem_specific": {
"urgency": "not yet assigned"
}
}
]Publisher severity
No explicit severity was provided.
- Event
- #56803 · Revision 1
- Added to Heist Feed
- Publisher date