CWE WEAKNESSES  /  CWE-147

CWE-147

Improper Neutralization of Input Terminators

What it is

The product receives input from an upstream component, but it does not neutralize or incorrectly neutralizes special elements that could be interpreted as input terminators when they are sent to a downstream component.

For example, a "." in SMTP signifies the end of mail message data, whereas a null character can be used for the end of a string.

Impact

Mitigations

• Developers should anticipate that terminators will be injected/removed/manipulated in the input vectors of their product. Use an appropriate combination of denylists and allowlists to ensure only valid, expected and appropriate input is processed by the system.
• [Implementation]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 r
• [Implementation] While it is risky to use dynamically-generated query strings, code, or commands that mix control and data together, sometimes it may be unavoidable. Properly quote arguments and escape any special characters within those arguments. The most conservative approach is to escape or filter all characters that do not pass an extremely strict allowlist (such as everything that is not alphanumeric or whit
• [Implementation] 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.

Real-world CVE examples

• CVE-2000-0319 — MFV. mail server does not properly identify terminator string to signify end of message, causing corruption, possibly in conjunction with off-by-one error.
• CVE-2000-0320 — MFV. mail server does not properly identify terminator string to signify end of message, causing corruption, possibly in conjunction with off-by-one error.
• CVE-2001-0996 — Mail server does not quote end-of-input terminator if it appears in the middle of a message.
• CVE-2002-0001 — Improperly terminated comment or phrase allows commands.

Related weaknesses

Source: MITRE CWE. View on cwe.mitre.org →