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Common Weakness Enumeration

A Community-Developed List of Software Weakness Types

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ID

CWE-33: Path Traversal: '....' (Multiple Dot)

Weakness ID: 33
Abstraction: Variant
Structure: Simple
Status: Incomplete
Presentation Filter:
+ Description
The software uses external input to construct a pathname that should be within a restricted directory, but it does not properly neutralize '....' (multiple dot) sequences that can resolve to a location that is outside of that directory.
+ Extended Description

This allows attackers to traverse the file system to access files or directories that are outside of the restricted directory.

The '....' manipulation is useful for bypassing some path traversal protection schemes. On some Windows systems, it is equivalent to "..\..\.." and might bypass checks that assume only two dots are valid. Incomplete filtering, such as removal of "./" sequences, can ultimately produce valid ".." sequences due to a collapse into unsafe value (CWE-182).

+ Relationships

The table(s) below shows the weaknesses and high level categories that are related to this weakness. These relationships are defined as ChildOf, ParentOf, MemberOf and give insight to similar items that may exist at higher and lower levels of abstraction. In addition, relationships such as PeerOf and CanAlsoBe are defined to show similar weaknesses that the user may want to explore.

+ Relevant to the view "Research Concepts" (CWE-1000)
NatureTypeIDName
ChildOfBaseBase23Relative Path Traversal
CanFollowBaseBase182Collapse of Data into Unsafe Value
+ Relevant to the view "Development Concepts" (CWE-699)
NatureTypeIDName
ChildOfBaseBase23Relative Path Traversal
+ Modes Of Introduction

The different Modes of Introduction provide information about how and when this weakness may be introduced. The Phase identifies a point in the software life cycle at which introduction may occur, while the Note provides a typical scenario related to introduction during the given phase.

PhaseNote
Implementation
+ Applicable Platforms
The listings below show possible areas for which the given weakness could appear. These may be for specific named Languages, Operating Systems, Architectures, Paradigms, Technologies, or a class of such platforms. The platform is listed along with how frequently the given weakness appears for that instance.

Languages

Class: Language-Independent (Undetermined Prevalence)

+ Common Consequences

The table below specifies different individual consequences associated with the weakness. The Scope identifies the application security area that is violated, while the Impact describes the negative technical impact that arises if an adversary succeeds in exploiting this weakness. The Likelihood provides information about how likely the specific consequence is expected to be seen relative to the other consequences in the list. For example, there may be high likelihood that a weakness will be exploited to achieve a certain impact, but a low likelihood that it will be exploited to achieve a different impact.

ScopeImpactLikelihood
Confidentiality
Integrity

Technical Impact: Read Files or Directories; Modify Files or Directories

+ Observed Examples
ReferenceDescription
read files via "/........../" in URL
read files via "...." in web server
read files via "......" in web server (doubled triple dot?)
read files via "......" in web server (doubled triple dot?)
multiple attacks using "..", "...", and "...." in different commands
"..." or "...." in chat server
+ Potential Mitigations

Phase: Implementation

Strategy: Input Validation

Assume all input is malicious. Use an "accept known good" input validation strategy, i.e., use a whitelist of acceptable inputs that strictly conform to specifications. Reject any input that does not strictly conform to specifications, or transform it into something that does.

When performing input validation, consider all potentially relevant properties, including length, type of input, the full range of acceptable values, missing or extra inputs, syntax, consistency across related fields, and conformance to business rules. As an example of business rule logic, "boat" may be syntactically valid because it only contains alphanumeric characters, but it is not valid if the input is only expected to contain colors such as "red" or "blue."

Do not rely exclusively on looking for malicious or malformed inputs (i.e., do not rely on a blacklist). A blacklist is likely to miss at least one undesirable input, especially if the code's environment changes. This can give attackers enough room to bypass the intended validation. However, blacklists can be useful for detecting potential attacks or determining which inputs are so malformed that they should be rejected outright.

When validating filenames, use stringent whitelists that limit the character set to be used. If feasible, only allow a single "." character in the filename to avoid weaknesses such as CWE-23, and exclude directory separators such as "/" to avoid CWE-36. Use a whitelist of allowable file extensions, which will help to avoid CWE-434.

Do not rely exclusively on a filtering mechanism that removes potentially dangerous characters. This is equivalent to a blacklist, which may be incomplete (CWE-184). For example, filtering "/" is insufficient protection if the filesystem also supports the use of "\" as a directory separator. Another possible error could occur when the filtering is applied in a way that still produces dangerous data (CWE-182). For example, if "../" sequences are removed from the ".../...//" string in a sequential fashion, two instances of "../" would be removed from the original string, but the remaining characters would still form the "../" string.

Phase: Implementation

Strategy: Input Validation

Inputs should be decoded and canonicalized to the application's current internal representation before being validated (CWE-180). Make sure that the application does not decode the same input twice (CWE-174). Such errors could be used to bypass whitelist validation schemes by introducing dangerous inputs after they have been checked.
+ Memberships
This MemberOf Relationships table shows additional CWE Categories and Views that reference this weakness as a member. This information is often useful in understanding where a weakness fits within the context of external information sources.
NatureTypeIDName
MemberOfCategoryCategory981SFP Secondary Cluster: Path Traversal
+ Notes

Maintenance

Like the triple-dot CWE-32, this manipulation probably hides multiple weaknesses that should be made more explicit.
+ Taxonomy Mappings
Mapped Taxonomy NameNode IDFitMapped Node Name
PLOVER'....' (multiple dot)
Software Fault PatternsSFP16Path Traversal
+ Content History
Submissions
Submission DateSubmitterOrganization
PLOVER
Modifications
Modification DateModifierOrganization
2008-07-01Eric DalciCigital
updated Potential_Mitigations, Time_of_Introduction
2008-09-08CWE Content TeamMITRE
updated Maintenance_Notes, Relationships, Taxonomy_Mappings
2008-10-14CWE Content TeamMITRE
updated Description, Maintenance_Notes
2009-07-27CWE Content TeamMITRE
updated Potential_Mitigations
2010-06-21CWE Content TeamMITRE
updated Description, Potential_Mitigations
2011-03-29CWE Content TeamMITRE
updated Potential_Mitigations
2011-06-01CWE Content TeamMITRE
updated Common_Consequences
2012-05-11CWE Content TeamMITRE
updated Relationships
2014-07-30CWE Content TeamMITRE
updated Relationships, Taxonomy_Mappings
2017-11-08CWE Content TeamMITRE
updated Applicable_Platforms
Previous Entry Names
Change DatePrevious Entry Name
2008-04-11Path Issue - Multiple Dot - '....'

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Page Last Updated: January 18, 2018