Weakness · High
CWE-647: Use of Non-Canonical URL Paths for Authorization Decisions
What it is
The product defines policy namespaces and makes authorization decisions based on the assumption that a URL is canonical. This can allow a non-canonical URL to bypass the authorization.
- Severity (our rating)
- High
- Likelihood of exploit
- High
- Introduced during
- Implementation, Operation
- Exploited in the wild
- 1 known exploited CVE
In more detail
If an application defines policy namespaces and makes authorization decisions based on the URL, but it does not require or convert to a canonical URL before making the authorization decision, then it opens the application to attack. For example, if the application only wants to allow access to http://www.example.com/mypage, then the attacker might be able to bypass this restriction using equivalent URLs such as: http://WWW.EXAMPLE.COM/mypage http://www.example.com/%6Dypage (alternate encoding) http://192.168.1.1/mypage (IP address) http://www.example.com/mypage/ (trailing /) http://www.example.com:80/mypage Therefore it is important to specify access control policy that is based on the path information in some canonical form with all alternate encodings rejected (which can be accomplished by a default deny rule).
What an attacker can do
- Bypass Protection Mechanism (Access Control)
- Read Files or Directories (Confidentiality)
How to prevent it
Architecture and Design
- Make access control policy based on path information in canonical form. Use very restrictive regular expressions to validate that the path is in the expected form.
- Reject all alternate path encodings that are not in the expected canonical form.
How to find it
- Automated Static Analysis. Automated static analysis, commonly referred to as Static Application Security Testing (SAST), can find some instances of this weakness by analyzing source code (or binary/compiled code) without having to execute it. Typically, this is done by building a model of data flow and control flow, then searching for potentially-vulnerable patterns that connect "sources" (origins of input) with "sinks" (destinations where the data interacts with external components, a lower layer such as the OS, etc.)
Exploited in the wild: 1 CVE
Vulnerabilities caused by CWE-647 that attackers have used, from CISA's Known Exploited Vulnerabilities catalog, newest first.
H2 Security
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Start freeSource: MITRE Common Weakness Enumeration, CWE version 4.19.1. CWE is a trademark of The MITRE Corporation.