CWE-1004: Sensitive Cookie Without 'HttpOnly' Flag

Extended Description

The HttpOnly flag directs compatible browsers to prevent client-side script from accessing cookies. Including the HttpOnly flag in the Set-Cookie HTTP response header helps mitigate the risk associated with Cross-Site Scripting (XSS) where an attacker's script code might attempt to read the contents of a cookie and exfiltrate information obtained. When set, browsers that support the flag will not reveal the contents of the cookie to a third party via client-side script executed via XSS.

Implementation

Leverage the HttpOnly flag when setting a sensitive cookie in a response.

Confidentiality

Read Application Data

If the HttpOnly flag is not set, then sensitive information stored in the cookie may be exposed to unintended parties.

Integrity

Gain Privileges or Assume Identity

If the cookie in question is an authentication cookie, then not setting the HttpOnly flag may allow an adversary to steal authentication data (e.g., a session ID) and assume the identity of the user.

Automated Static Analysis

Effectiveness: High

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.)