How severe is CVE-2026-33306?

No CVSS score has been assigned to CVE-2026-33306 yet. Review the advisory details and affected package list to assess your exposure.

Which packages are affected by CVE-2026-33306?

CVE-2026-33306 affects the following packages: bcrypt (RubyGems). Ecosystems affected: RubyGems.

How do I fix CVE-2026-33306?

Update bcrypt to 3.1.22 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-33306 is resolved across your whole dependency graph.

How do I detect CVE-2026-33306 in my RubyGems dependencies?

Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for bcrypt, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

How do I mitigate CVE-2026-33306 if there is no patch (or I can't update yet)?

Constrain what reaches the vulnerable code: limit the size and shape of untrusted input, isolate the affected component in a sandboxed or least-privileged process, and enable the platform's memory-safety mitigations (ASLR, stack protector, hardened allocator) so an out-of-bounds access is more likely to fail closed than to be exploitable.

Is CVE-2026-33306 actively exploited in the wild?

No public exploit code has been indexed for CVE-2026-33306 yet. This does not mean the vulnerability cannot be exploited — absence of public exploits does not imply safety. Apply the recommended fix and use O3 Security to monitor your exposure.

What is the EPSS score for CVE-2026-33306?

CVE-2026-33306 has an EPSS (Exploit Prediction Scoring System) score of 0.2%, placing it in the 15th percentile of all CVEs. EPSS is maintained by FIRST.org and estimates the probability that a vulnerability will be exploited in the wild within the next 30 days. This score indicates relatively lower exploitation probability, though the CVSS severity should still guide your patching priority.

What type of vulnerability is CVE-2026-33306?

CVE-2026-33306 is classified as CWE-190 (CWE-190). This weakness type describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation.

When was CVE-2026-33306 published, and has it been updated?

CVE-2026-33306 was published on March 24, 2026 and was last updated on October 28, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

CVE-2026-33306: bcrypt — Fixed in 3.1.22

Exploitation Status

No confirmed exploitation observed yet

CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.

Exploitation and automatability from CISA’s SSVC triage for CVE-2026-33306.

EPSS Exploitation Probability

via FIRST.org ↗

0.2%probability of exploitation in next 30 days

Lower Risk0.00%

Lower risk than most CVEs15th percentile — riskier than 15% of all scored CVEsHighest risk

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

Real-World Exposure

1 pkg affected

💎bcrypt

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects RubyGems packages — download data is not available via public APIs for these ecosystems.

Description

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.

Affected Packages

1 total 1 fixed

Ecosystem	Package	Vulnerable range	Fix
💎RubyGems	`bcrypt`	all versions	3.1.22`bundle update bcrypt --conservative`

Affected Products

1 product · 1 configurations

Application

bcrypt-rubybcrypt-ruby_project

< 3.1.22

range

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for bcrypt, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update bcrypt to 3.1.22 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-33306 is resolved across your whole dependency graph.
Workarounds
Constrain what reaches the vulnerable code: limit the size and shape of untrusted input, isolate the affected component in a sandboxed or least-privileged process, and enable the platform's memory-safety mitigations (ASLR, stack protector, hardened allocator) so an out-of-bounds access is more likely to fail closed than to be exploitable.

Frequently Asked Questions

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**. T

O3 Security · Impact-Aware SCA

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CVE-2026-33306 — bcrypt