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CVE-2017-6181

HIGH · 7.5 CVSS v3.0 Published 2017-04-03
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
84/100
Remediation priority · High
Remotely reachable No privileges Zero-click

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
The parse_char_class function in regparse.c in the Onigmo (aka Oniguruma-mod) regular expression library, as used in Ruby 2.4.0, allows remote attackers to cause a denial of service (deep recursion and application crash) via a crafted regular expression.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · high confidence

A crafted regular expression triggers deep recursion in the parse_char_class function in Onigmo (Oniguruma-mod) regex library as used in Ruby 2.4.0, causing stack overflow and denial of service. The vulnerability stems from insufficient recursion depth handling during character class parsing.

MitigationUpgrade Ruby to a version newer than 2.4.0 that includes the patched Onigmo library, or apply the upstream Onigmo patch that adds recursion limits to parse_char_class.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
RubyApplication
Affected:= 2.4.0

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High

CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Determine installed Ruby version
    Run 'ruby --version' or 'ruby -v' in the command line to retrieve the exact Ruby interpreter version
    Affected if The version displayed is exactly 2.4.0, as this is the sole affected version for this CVE
  2. Verify Onigmo regex engine is in use
    Ruby 2.4.0 uses the Onigmo regex library by default. Confirm by checking Ruby's regex engine: ruby -e "puts Regexp::Engine"
    Affected if The engine reports as Onigmo, indicating the vulnerable library is in use
  3. Confirm Ruby was built with Oniguruma extension
    Run ruby -e "puts defined?(Oniguruma) ? 'Oniguruma present' : 'Not present'" to check if Oniguruma support is compiled in
    Affected if Oniguruma/Onigmo support is present, which is the default in Ruby 2.4.0 and required for the parse_char_class vulnerability to be triggered

You are affected if your Ruby installation is exactly version 2.4.0 with Onigmo/Oniguruma regex support enabled, as the vulnerability exists only in this specific version.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

From vendor data
Mitigation available No clean upgrade yet — mitigate in the meantime
Mitigation

Upgrade Ruby to a version newer than 2.4.0 that includes the patched Onigmo library, or apply the upstream Onigmo patch that adds recursion limits to parse_char_class.

Fix this in Ruby Scoped from the published advisory
  • Consultation2.0 h
  • Implementation3.0 h
  • Testing2.0 h
  • Review / QA1.0 h
8.0 hours of engineering $1,420
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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2017-6181 in production — separate from our analysis above.

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
  • No weaponised exploit code, or anything meant to cause harm
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