CAPEC-3 · Using Leading 'Ghost' Character Sequences to Bypass Input Filters

Scaner-VSvulnerability catalog · v4.2

CAPEC-3DetailedDraft

Abstraction: Detailed

Status: Draft

Using Leading 'Ghost' Character Sequences to Bypass Input Filters

Some APIs will strip certain leading characters from a string of parameters. An adversary can intentionally introduce leading "ghost" characters (extra characters that don't affect the validity of the request at the API layer) that enable the input to pass the filters and therefore process the adversary's input. This occurs when the targeted API will accept input data in several syntactic forms and interpret it in the equivalent semantic way, while the filter does not take into account the full spectrum of the syntactic forms acceptable to the targeted API.

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Related CWEs

The product receives input or data, but it does.

The product is vulnerable to file system contents disclosure through path equivalence.

The product constructs all or part of a command, data structure, or record using externally-influenced input from an upstream component, but it does not neutralize or incorrectly neutralizes special elements that could modify how it is pars

The product does not properly encode or decode the data, resulting in unexpected values.

The product does not properly handle when an input uses an alternate encoding that is valid for the control sphere to which the input is being sent.

The product validates input before applying protection mechanisms that modify the input, which could allow an attacker to bypass the validation via dangerous inputs that only arise after the modification.

The product validates input before it is canonicalized, which prevents the product from detecting data that becomes invalid after the canonicalization step.

The product validates data before it has been filtered, which prevents the product from detecting data that becomes invalid after the filtering step.

The product implements a protection mechanism that relies on a list of inputs (or properties of inputs) that are explicitly allowed by policy because the inputs are assumed to be safe, but the list is too permissive - that is, it allows an

The product implements a protection mechanism that relies on a list of inputs (or properties of inputs) that are not allowed by policy or otherwise require other action to neutralize before additional processing takes place, but the list is

The product compares two entities in a security-relevant context, but the comparison is incorrect.

The product does not ensure or incorrectly ensures that structured messages or data are well-formed and that certain security properties are met before being read from an upstream component or sent to a downstream component.

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