CWE-27: Path Traversal: 'dir/../../filename'

Extended Description

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.

Source-backed guidance

Additional facts reviewed against primary or authoritative security sources.

Verify controls for CWE-27 with SSDF evidence

Use NIST SSDF verification and vulnerability-response practices to detect CWE-27, Path Traversal: 'dir/../../filename', throughout the product lifecycle. Derive review questions, static or dynamic checks, and negative tests from the CWE's causal behavior; define the components and lifecycle stages each check covers; and retain findings with enough evidence to distinguish the root cause from symptoms and impacts. Track escapes and false negatives, then improve the verification plan after every confirmed occurrence.

NIST SP 800-218 Secure Software Development Framework — National Institute of Standards and Technology

Apply Input Validation controls for Path Traversal: 'dir/../../filename'

MITRE associates mitigation with Implementation; the listed strategies include Input Validation; documented detection approaches include Automated Static Analysis. Use these source-defined anchors to turn CWE-27 into implementation, review, and verification checks for the affected component.

CWE-27: Path Traversal: 'dir/../../filename' — MITRE CWE

Triage CWE-27 against known exploitation evidence

Use CISA's Known Exploited Vulnerabilities catalog to test whether a vulnerability mapped to CWE-27, Path Traversal: 'dir/../../filename', has evidence of exploitation in the wild. Confirm the CVE-to-CWE root-cause mapping independently before attaching the example, then capture the affected product, required action, and remediation deadline. A missing KEV match is not evidence that the weakness is unexploited, and a KEV entry must not be generalized to every occurrence of this CWE.

Known Exploited Vulnerabilities Catalog — Cybersecurity and Infrastructure Security Agency

Apply precise root-cause mapping to CWE-27

Apply MITRE's full root-cause mapping guidance when using CWE-27, Path Traversal: 'dir/../../filename'. Separate weakness language from attacker prerequisites and technical impact, check the entry's abstraction and vulnerability-mapping notes, and prefer the most specific Base or Variant supported by the evidence. Record the rejected alternatives and require an independent review before the mapping is used for remediation trends or program metrics.

CVE to CWE Root Cause Mapping Guidance — MITRE CWE

Validate CWE-27 with root-cause mapping checks

Apply MITRE's root-cause mapping quick tips to CWE-27, Path Traversal: 'dir/../../filename'. Confirm the finding describes the causal weakness rather than an impact or attack pattern, compare the abstraction and mapping notes with plausible alternatives, and have a second reviewer challenge the selection. Preserve the evidence and reasoning so recurring defects can be measured against one consistent identifier.

CVE to CWE Root Cause Mapping Quick Tips — MITRE CWE

Frequently Asked Questions

What is CWE-27: Path Traversal: 'dir/../../filename'?+

CWE-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.

What are the security consequences of Path Traversal: 'dir/../../filename'?+

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.

Which programming languages are affected by Path Traversal: 'dir/../../filename'?+

CWE-27 commonly affects Not Language-Specific. Note that weaknesses are often language-agnostic patterns, so secure coding practices apply broadly.

What are real-world examples of Path Traversal: 'dir/../../filename'?+

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.

What is the difference between a CWE and a CVE?+

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.

CWE-27: Path Traversal: 'dir/../../filename'

Extended Description

Technical Details

Applicable To

Security Consequences

Scope

Impact

Mitigation Strategies

Detection Methods

Code Examples & CVEs

Observed CVE Examples (1)

CWE Relationships

Parent Weaknesses