Weakness · Medium
CWE-93: Improper Neutralization of CRLF Sequences ('CRLF Injection')
What it is
The product uses CRLF (carriage return line feeds) as a special element, e.g. to separate lines or records, but it does not neutralize or incorrectly neutralizes CRLF sequences from inputs.
- Severity (our rating)
- Medium
- Likelihood of exploit
- Not rated by MITRE
- Introduced during
- Implementation
- Exploited in the wild
- 1 known exploited CVE
What an attacker can do
- Modify Application Data (Integrity)
How to prevent it
Implementation
- Avoid using CRLF as a special sequence.
- Appropriately filter or quote CRLF sequences in user-controlled input.
While the code is being fixed, a WAF in blocking mode stops CRLF injection in headers and parameters at the edge.
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-93 that attackers have used, from CISA's Known Exploited Vulnerabilities catalog, newest first.
The Dome
Block it at the edge while you fix it
The Dome's WAF runs the OWASP Core Rule Set in blocking mode and stops CRLF injection in headers and parameters before they reach your application.
See the DomeT Academy
Stop writing it in the first place
Learn to build software and systems without weaknesses like this one, with practice on real hosts in your browser, every objective checked on the machine.
Start freeSource: MITRE Common Weakness Enumeration, CWE version 4.19.1. CWE is a trademark of The MITRE Corporation.