The application does not conform to the API requirements for a
function call that requires extra privileges. This could allow attackers to gain
privileges by causing the function to be called
incorrectly.
Extended Description
When an application contains certain functions that perform operations
requiring an elevated level of privilege, the caller of a privileged API
must be careful to:
- ensure that assumptions made by the APIs is valid, such as validity
of arguments
- account for known weaknesses in the design/implementation of the
API
- call the API from a safe context
If the caller of the API does not follow these requirements, then it may
allow a malicious user or process to elevate their privilege, hijack the
process, or steal sensitive data.
For instance, it is important to know if privileged APIs fail to properly
shed their privileges before returning to the caller or if the privileged
function might make certain assumptions about the data, context or state
information passed to it by the caller. It is important to always know when
and how privileged APIs can be called in order to ensure that their elevated
level of privilege cannot be exploited.
Time of Introduction
Architecture and Design
Implementation
Operation
Applicable Platforms
Languages
All
Common Consequences
Scope
Effect
Access Control
Elevation of privilege
Confidentiality
Information disclosure
Integrity
Arbitrary code execution
Likelihood of Exploit
Low
Enabling Factors for Exploitation
An application contains functions running processes that hold higher
privileges.
There is code in the application that calls the privileged APIs.
There is a way for a user to control the data that is being passed to the
privileged API or control the context from which it is being called.
Observed Examples
Reference
Description
From http://xforce.iss.net/xforce/xfdb/12848:
man-db is a Unix utility that displays online help files. man-db versions
2.3.12 beta and 2.3.18 to 2.4.1 could allow a local attacker to gain
privileges, caused by a vulnerability when the open cat stream function is
called. If man-db is installed setuid, a local attacker could exploit this
vulnerability to gain "man" user privileges.
Potential Mitigations
Phase
Description
Implementation
Before calling privileged APIs, always ensure that the assumptions
made by the privileged code hold true prior to making the call.
Know architecture and implementation weaknesses of the privileged APIs
and make sure to account for these weaknesses before calling the
privileged APIs to ensure that they can be called safely.
If privileged APIs make certain assumptions about data, context or
state validity that are passed by the caller, the calling code must
ensure that these assumptions have been validated prior to making the
call.
If privileged APIs fail to shed their privilege prior to returning to
the calling code, then calling code needs to shed these privileges
immediately and safely right after the call to the privileged APIs. In
particular, the calling code needs to ensure that a privileged thread of
execution will never be returned to the user or made available to
user-controlled processes.
Only call privileged APIs from safe, consistent and expected state.
Ensure that a failure or an error will not leave a system in a state
where privileges are not properly shed and privilege escalation is
possible (i.e. fail securely with regards to handling of privileges).
Description
