COMMON WEAKNESS ENUMERATIONDraft

CWE-591

Sensitive Data Storage in Improperly Locked Memory

The product stores sensitive data in memory that is not locked, or that has been incorrectly locked, which might cause the memory to be written to swap files on disk by the virtual memory manager. This can make the data more accessible to external actors.

Abstraction

Variant

Structure

Simple

Likelihood of Exploit

Medium

Understand the problem

What is the problem?

The product stores sensitive data in memory that is not locked, or that has been incorrectly locked, which might cause the memory to be written to swap files on disk by the virtual memory manager. This can make the data more accessible to external actors.

Extended description

On Windows systems the VirtualLock function can lock a page of memory to ensure that it will remain present in memory and not be swapped to disk. However, on older versions of Windows, such as 95, 98, or Me, the VirtualLock() function is only a stub and provides no protection. On POSIX systems the mlock() call ensures that a page will stay resident in memory but does not guarantee that the page will not appear in the swap. Therefore, it is unsuitable for use as a protection mechanism for sensitive data. Some platforms, in particular Linux, do make the guarantee that the page will not be swapped, but this is non-standard and is not portable. Calls to mlock() also require supervisor privilege. Return values for both of these calls must be checked to ensure that the lock operation was actually successful.

Root cause

How and when does the problem arise?

Lifecycle phase

Implementation

Risk

What does successful exploitation lead to?

Read Application DataRead Memory

Affected security scopes: Confidentiality

Sensitive data that is written to a swap file may be exposed.

Defence

How is it prevented and fixed?

Architecture and Design

Architecture and design approach

Detail
Identify data that needs to be protected from swapping and choose platform-appropriate protection mechanisms.

Implementation

Implementation-phase defence

Detail
Check return values to ensure locking operations are successful.