WebrickApplication · Ruby Lang
CVE-2019-11879
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 · uneditedThe WEBrick gem 1.4.2 for Ruby allows directory traversal if the attacker once had local access to create a symlink to a location outside of the web root directory. NOTE: The vendor states that this is analogous to Options FollowSymlinks in the Apache HTTP Server, and therefore it is "not a problem.
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 · moderate confidenceWEBrick 1.4.2 for Ruby contains a directory traversal vulnerability where the server follows symlinks that point outside the web root directory, allowing unauthorized access to arbitrary files on the filesystem. The attack requires prior local access to create a malicious symlink within the web root.
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
WebrickApplication
= 1.4.2CVSS 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
- Local
- Complexity
- Low
- Privileges
- Low
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- High
- Integrity
- None
- Availability
- None
CVSS:3.0/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N
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 checksWork through these to decide whether this CVE applies to you.
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Identify installed WEBrick versionRun 'gem list webrick' or 'ruby -e "require 'webrick'; puts WEBrick::VERSION"' to confirm version 1.4.2 is installedAffected if WEBrick version 1.4.2 is confirmed installed
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Locate WEBrick server configurationSearch project directories for WEBrick configuration files (often in config/ or app files) containing :DocumentRoot or :FollowSymLinks settingsAffected if Configuration enables FollowSymLinks without restriction
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Check if FollowSymLinks is enabled in WEBrick configInspect WEBrick config hash for :FollowSymLinks => true or similar setting in the server startup configurationAffected if FollowSymLinks option is explicitly set to true or permitted
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Verify file permissions on web root directoryCheck ownership and permissions on the DocumentRoot directory using 'ls -la' - look for world-writable or group-writable permissions that could allow untrusted users to create symlinksAffected if Web root directory has permissive write permissions allowing untrusted local users to add files or symlinks
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Scan for unexpected symlinks in web-accessible pathsRun 'find /path/to/documentroot -type l -ls' to enumerate all symlinks within the web root directoryAffected if Symlinks exist that point outside the document root to sensitive system paths
Environment is affected if WEBrick 1.4.2 is running with FollowSymLinks enabled and the web root has permissions allowing untrusted local users to create symlinks pointing to sensitive files outside the web root.
Generated from the published advisory. Verify against your own configuration.
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 dataConfigure WEBrick to disable symlink following or ensure strict permissions preventing untrusted users from creating symlinks in web-accessible directories.
Fix this in Webrick
Scoped from the published advisory
- Consultation2.0 h
- Implementation2.0 h
- Testing2.0 h
- Review / QA1.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $1,984.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2019-11879 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.
References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.
Primary sourcesPractitioner notes
ContributedPeer-ranked notes from engineers who’ve handled CVE-2019-11879 in production — separate from our analysis above.
The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.
- The version that genuinely resolved it — not the one the vendor claimed
- A config change or rule that shut the vector down
- A gotcha in the upgrade path that cost you an afternoon
No notes yet
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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.
- 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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