Directory traversal vulnerability in WEBrick in Ruby 1.8 before 1.8.5-p115 and 1.8.6-p114, and 1.9 through 1.9.0-1, when running on systems

Affected versions

NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.

• fedoraproject fedora7
• fedoraproject fedora8
• ruby-lang webrickall versions

Package-level exposure

OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.

Other highest-scoring records for the same primary product.

• CVE-2009-4492WEBrick 1.3.1 in Ruby 1.8.6 through patchlevel 383, 1.8.7 through patchlevel 248, 1.8.8dev, 1.9.1 through patchlevel 376, and 1.9.2dev write
  35Monitor
• CVE-2025-6442Ruby WEBrick read_header HTTP Request Smuggling Vulnerability
  23Monitor
• CVE-2019-11879The 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
  22Monitor

FIRST EPSS daily score; only changes of 0.01 or more are recorded (step chart).

Root cause

A user-supplied file name is joined with the allowed directory, but the result is never checked to confirm it is still inside that directory.

A representative example of this vulnerability class. Not the vendor's source code; it shows the faulty pattern and its fix.

1const file = path.join(ROOT, req.query.name);2res.sendFile(file);

1const file = path.resolve(ROOT, req.query.name);2if (!file.startsWith(ROOT + path.sep)) {3  return res.sendStatus(400);4}5res.sendFile(file);

Attack context

MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.