CWE-1286

入力の構文的正しさの不適切な検証

Improper Validation of Syntactic Correctness of Input

脆弱性作成中

日本語説明

この製品は、整形式であることが期待される入力、すなわち特定の構文に準拠する入力を受け取るが、その入力が構文に準拠しているかどうかを検証しないか、誤って検証する。

多くの場合、複雑な入力は特定の構文に従うことが期待され、それは入力自体が想定しているか、ヘッダーなどのメタデータの中で宣言されている。その構文とは、データ交換フォーマット、マークアップ言語、あるいはプログラミング言語などである。信頼されない入力が期待される構文に対して適切に検証されない場合、攻撃者は解析の失敗を引き起こしたり、予期しないエラーを引き起こしたり、入力が構文に適合していれば直接悪用できないかもしれない潜在的な脆弱性を露呈させたりする可能性がある。

原文 (English)

The product receives input that is expected to be well-formed - i.e., to comply with a certain syntax - but it does not validate or incorrectly validates that the input complies with the syntax.

Often, complex inputs are expected to follow a particular syntax, which is either assumed by the input itself, or declared within metadata such as headers. The syntax could be for data exchange formats, markup languages, or even programming languages. When untrusted input is not properly validated for the expected syntax, attackers could cause parsing failures, trigger unexpected errors, or expose latent vulnerabilities that might not be directly exploitable if the input had conformed to the syntax.

関連する脆弱性

想定される影響

Scope: Other / Impact: Varies by Context

対策・緩和策

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.

外部リンク

MITRE公式ページ — CWE-1286