Absolute Path Traversal

Opis

The product uses external input to construct a pathname that should be within a restricted directory, but it does not properly neutralize absolute path sequences such as "/abs/path" 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.

Skutki

• Integrity, Confidentiality, Availability

  Execute Unauthorized Code or Commands

  The attacker may be able to create or overwrite critical files that are used to execute code, such as programs or libraries.

• Integrity

  Modify Files or Directories

  The attacker may be able to overwrite or create critical files, such as programs, libraries, or important data. If the targeted file is used for a security mechanism, then the attacker may be able to bypass that mechanism. For example, appending a new account at the end of a password file may allow an attacker to bypass authentication.

• Confidentiality

  Read Files or Directories

  The attacker may be able read the contents of unexpected files and expose sensitive data. If the targeted file is used for a security mechanism, then the attacker may be able to bypass that mechanism. For example, by reading a password file, the attacker could conduct brute force password guessing attacks in order to break into an account on the system.

• Availability

  DoS: Crash, Exit, or Restart

  The attacker may be able to overwrite, delete, or corrupt unexpected critical files such as programs, libraries, or important data. This may prevent the product from working at all and in the case of a protection mechanisms such as authentication, it has the potential to lockout every user of the product.

Zapobieganie

• Implementation · 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.

  Skuteczność: High

• Implementation · 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 allowlist validation schemes by introducing dangerous inputs after they have been checked.

• Operation · Firewall

  Use an application firewall that can detect attacks against this weakness. It can be beneficial in cases in which the code cannot be fixed (because it is controlled by a third party), as an emergency prevention measure while more comprehensive software assurance measures are applied, or to provide defense in depth [REF-1481].

  Skuteczność: Moderate

Przykłady podatności

• CVE-2024-0520 Product for managing datasets for AI model training and evaluation allows both relative (CWE-23) and absolute (CWE-36) path traversal to overwrite files via the Content-Disposition header
• CVE-2022-31503 Python package constructs filenames using an unsafe os.path.join call on untrusted input, allowing absolute path traversal because os.path.join resets the pathname to an absolute path that is specified as part of the input.
• CVE-2002-1345 Multiple FTP clients write arbitrary files via absolute paths in server responses
• CVE-2001-1269 ZIP file extractor allows full path
• CVE-2002-1818 Path traversal using absolute pathname
• CVE-2002-1913 Path traversal using absolute pathname
• CVE-2005-2147 Path traversal using absolute pathname
• CVE-2000-0614 Arbitrary files may be overwritten via compressed attachments that specify absolute path names for the decompressed output.
• CVE-1999-1263 Mail client allows remote attackers to overwrite arbitrary files via an e-mail message containing a uuencoded attachment that specifies the full pathname for the file to be modified.
• CVE-2003-0753 Remote attackers can read arbitrary files via a full pathname to the target file in config parameter.
• CVE-2002-1525 Remote attackers can read arbitrary files via an absolute pathname.
• CVE-2001-0038 Remote attackers can read arbitrary files by specifying the drive letter in the requested URL.
• CVE-2001-0255 FTP server allows remote attackers to list arbitrary directories by using the "ls" command and including the drive letter name (e.g. C:) in the requested pathname.
• CVE-2001-0933 FTP server allows remote attackers to list the contents of arbitrary drives via a ls command that includes the drive letter as an argument.
• CVE-2002-0466 Server allows remote attackers to browse arbitrary directories via a full pathname in the arguments to certain dynamic pages.
• CVE-2002-1483 Remote attackers can read arbitrary files via an HTTP request whose argument is a filename of the form "C:" (Drive letter), "//absolute/path", or ".." .
• CVE-2004-2488 FTP server read/access arbitrary files using "C:\" filenames
• CVE-2001-0687 FTP server allows a remote attacker to retrieve privileged web server system information by specifying arbitrary paths in the UNC format (\\computername\sharename).

Słabość nadrzędna

• CWE-22 Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal')

Słabości podrzędne

• CWE-37 Path Traversal: '/absolute/pathname/here'
• CWE-38 Path Traversal: '\absolute\pathname\here'
• CWE-39 Path Traversal: 'C:dirname'
• CWE-40 Path Traversal: '\\UNC\share\name\' (Windows UNC Share)

Kiedy powstaje

• Implementation

Dotyczy

Not Language-Specific, Not Technology-Specific, Web Based, AI/ML

Źródła

1. The Art of Software Security Assessment — Mark Dowd, John McDonald, Justin Schuh, Chapter 9, "Filenames and Paths", Page 503, Addison Wesley, 2006
2. Secure by Design Alert: Eliminating Directory Traversal Vulnerabilities in Software — Cybersecurity and Infrastructure Security Agency, 2024
3. D3FEND: Application Layer Firewall — D3FEND