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💎 RubyGems
Not in CISA KEV
HIGH severity

CVE-2009-4123 — jruby-openssl

HIGH

CVE-2009-4123 is a high-severity (CVSS 7.5) CWE-295 vulnerability in jruby-openssl. A fix is available for jruby-openssl — see the affected versions and patch details below.

jruby-openssl gem for JRuby fails to do proper certificate validation

Published
Updated
Affected
1 pkg
Patched
1 / 1
Exploits
None indexed
Exploitation data as of Oct 30, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

EPSS Exploitation Probability

via FIRST.org ↗
0.6%probability of exploitation in next 30 days
Lower Risk0.00%
Lower risk than most CVEs49th percentile — riskier than 49% of all scored CVEsHighest risk
0.00%0.37%0.73%1.10%0.3%0.6%Apr 26Aug 26Oct 26

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

How urgent is this, really

Where this sits among everything scored

Real-World Exposure

1 pkg affected
💎jruby-openssl

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

A security problem involving peer certificate verification was found where failed verification silently did nothing, making affected applications vulnerable to attackers. Attackers could lead a client application to believe that a secure connection to a rogue SSL server is legitimate. Attackers could also penetrate client-validated SSL server applications with a dummy certificate.

Affected Packages

1 total 1 fixed
EcosystemPackageVulnerable rangeFix
💎RubyGemsjruby-opensslall versions0.6bundle update jruby-openssl --conservative

Affected Products

1 product · 1 configurations
Application
jruby-openssljruby
< 0.6
range

Detection & mitigation playbook

Open-source dependency

  1. Detect

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

  2. Fix

    Update jruby-openssl to 0.6 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2009-4123 is resolved across your whole dependency graph.

  3. Workarounds

    If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.

Frequently Asked Questions

A security problem involving peer certificate verification was found where failed verification silently did nothing, making affected applications vulnerable to attackers. Attackers could lead a client application to believe that a secure connection to a rogue SSL server is legitimate. Attackers could also penetrate client-validated SSL server applications with a dummy certificate.
O3 Security · Impact-Aware SCA

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CVE-2009-4123: jruby-openssl — Fixed in 0.6