The product uses external input to construct a pathname that should be within a restricted directory, but it does not properly neutralize multiple internal "../" sequences that can resolve to a location that is outside of that directory.
View on MITREThis allows attackers to traverse the file system to access files or directories that are outside of the restricted directory. The 'directory/../../filename' manipulation is useful for bypassing some path traversal protection schemes. Sometimes a program only removes one "../" sequence, so multiple "../" can bypass that check. Alternately, this manipulation could be used to bypass a check for "../" at the beginning of the pathname, moving up more than one directory level.
No mitigation information available for this CWE.
No detection method information available for this CWE.
Server allows remote attackers to cause a denial of service via certain HTTP GET requests containing a %2e%2e (encoded dot-dot), several "/../" sequences, or several "../" in a URI.
View DetailsCWE-27: Path Traversal: 'dir/../../filename' is a Common Weakness Enumeration (CWE) entry maintained by MITRE. The product uses external input to construct a pathname that should be within a restricted directory, but it does not properly neutralize multiple internal "../" sequences that can resolve to a location that is outside of that directory. This allows attackers to traverse the file system to access files or directories that are outside of the restricted directory. The 'directory/../../filename' manipulation is useful for bypassing some path traversal protection schemes. Sometimes a program only removes one "../" sequence, so multiple "../" can bypass that check. Alternately, this manipulation could be used to bypass a check for "../" at the beginning of the pathname, moving up more than one directory level.
If exploited, CWE-27 (Path Traversal: 'dir/../../filename') it can compromise Confidentiality and Integrity, leading to outcomes such as Read Files or Directories and Modify Files or Directories.
CWE-27 commonly affects Not Language-Specific. Note that weaknesses are often language-agnostic patterns, so secure coding practices apply broadly.
MITRE documents real CVEs mapped to CWE-27, including CVE-2002-0298. You can look up the full details of each CVE, including CVSS scores and remediation guidance, on our CVE Lookup tool.
A CWE (Common Weakness Enumeration) like CWE-27 describes a category of software weakness — the underlying flaw type. A CVE (Common Vulnerabilities and Exposures) identifies a specific, real-world vulnerability in a particular product. In short, a CWE is the kind of mistake, and a CVE is an instance of that mistake being found in software.