81
Weakness ID : 38
Structure : Simple
Abstraction : Variant
Description
The product accepts input in the form of a backslash absolute path ('\absolute\pathname\here')
without appropriate validation, which can allow an attacker to traverse the file system to unintended
locations or access arbitrary files.
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, MemberOr 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 may want to be explored.
Relevant to the view "Research Concepts" (CWE-1000)
Nature Type ID Name Page
ChildOf 36 Absolute Path Traversal 75
Applicable Platforms
Language : Not Language-Specific (Prevalence = Undetermined)
Common Consequences
Scope Impact Likelihood
Confidentiality
Integrity
Read Files or Directories
Modify Files or Directories
Potential Mitigations
Phase: Implementation
Strategy = Input Validation
Assume all input is malicious. Use an "accept known good" input validation strategy, i.e., use
a list 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. This 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, denylists 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 allowlists 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 list 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 denylist, 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.
Effectiveness = High
Phase: Implementation
CWE Version 4.14
CWE-39: Path Traversal: 'C:dirname'
CWE-39: Path Traversal: 'C:dirname'