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ID

CWE-822: Untrusted Pointer Dereference

Weakness ID: 822
Abstraction: Base
Structure: Simple
Status: Incomplete
Presentation Filter:
+ Description
The program obtains a value from an untrusted source, converts this value to a pointer, and dereferences the resulting pointer.
+ Extended Description

An attacker can supply a pointer for memory locations that the program is not expecting. If the pointer is dereferenced for a write operation, the attack might allow modification of critical program state variables, cause a crash, or execute code. If the dereferencing operation is for a read, then the attack might allow reading of sensitive data, cause a crash, or set a program variable to an unexpected value (since the value will be read from an unexpected memory location).

There are several variants of this weakness, including but not necessarily limited to:

  • The untrusted value is directly invoked as a function call.
  • In OS kernels or drivers where there is a boundary between "userland" and privileged memory spaces, an untrusted pointer might enter through an API or system call (see CWE-781 for one such example).
  • Inadvertently accepting the value from an untrusted control sphere when it did not have to be accepted as input at all. This might occur when the code was originally developed to be run by a single user in a non-networked environment, and the code is then ported to or otherwise exposed to a networked environment.
+ Relationships

The table(s) below shows the weaknesses and high level categories that are related to this weakness. These relationships are defined as ChildOf, ParentOf, MemberOf and give insight to similar items that may exist at higher and lower levels of abstraction. In addition, relationships such as PeerOf and CanAlsoBe are defined to show similar weaknesses that the user may want to explore.

+ Relevant to the view "Research Concepts" (CWE-1000)
+ Relevant to the view "Development Concepts" (CWE-699)
+ Common Consequences

The table below specifies different individual consequences associated with the weakness. The Scope identifies the application security area that is violated, while the Impact describes the negative technical impact that arises if an adversary succeeds in exploiting this weakness. The Likelihood provides information about how likely the specific consequence is expected to be seen relative to the other consequences in the list. For example, there may be high likelihood that a weakness will be exploited to achieve a certain impact, but a low likelihood that it will be exploited to achieve a different impact.

ScopeImpactLikelihood
Confidentiality

Technical Impact: Read Memory

If the untrusted pointer is used in a read operation, an attacker might be able to read sensitive portions of memory.
Availability

Technical Impact: DoS: Crash, Exit, or Restart

If the untrusted pointer references a memory location that is not accessible to the program, or points to a location that is "malformed" or larger than expected by a read or write operation, the application may terminate unexpectedly.
Integrity
Confidentiality
Availability

Technical Impact: Execute Unauthorized Code or Commands; Modify Memory

If the untrusted pointer is used in a function call, or points to unexpected data in a write operation, then code execution may be possible.
+ Observed Examples
ReferenceDescription
message-passing framework interprets values in packets as pointers, causing a crash.
labeled as a "type confusion" issue, also referred to as a "stale pointer." However, the bug ID says "contents are simply interpreted as a pointer... renderer ordinarily doesn't supply this pointer directly". The "handle" in the untrusted area is replaced in one function, but not another - thus also, effectively, exposure to wrong sphere (CWE-668).
Untrusted dereference using undocumented constructor.
An error code is incorrectly checked and interpreted as a pointer, leading to a crash.
An untrusted value is obtained from a packet and directly called as a function pointer, leading to code execution.
Undocumented attribute in multimedia software allows "unmarshaling" of an untrusted pointer.
ActiveX control for security software accepts a parameter that is assumed to be an initialized pointer.
Spreadsheet software treats certain record values that lead to "user-controlled pointer" (might be untrusted offset, not untrusted pointer).
+ Memberships
This MemberOf Relationships table shows additional CWE Categories and Views that reference this weakness as a member. This information is often useful in understanding where a weakness fits within the context of external information sources.
+ Notes

Maintenance

There are close relationships between incorrect pointer dereferences and other weaknesses related to buffer operations. There may not be sufficient community agreement regarding these relationships. Further study is needed to determine when these relationships are chains, composites, perspective/layering, or other types of relationships. As of September 2010, most of the relationships are being captured as chains.

Research Gap

Under-studied and probably under-reported as of September 2010. This weakness has been reported in high-visibility software, but applied vulnerability researchers have only been investigating it since approximately 2008, and there are only a few public reports. Few reports identify weaknesses at such a low level, which makes it more difficult to find and study real-world code examples.

Terminology

Many weaknesses related to pointer dereferences fall under the general term of "memory corruption" or "memory safety." As of September 2010, there is no commonly-used terminology that covers the lower-level variants.
+ Content History
Submissions
Submission DateSubmitterOrganization
2010-09-22CWE Content TeamMITRE
Modifications
Modification DateModifierOrganization
2011-03-29CWE Content TeamMITRE
updated Description
2011-06-01CWE Content TeamMITRE
updated Common_Consequences
2011-06-27CWE Content TeamMITRE
updated Related_Attack_Patterns, Relationships
2011-09-13CWE Content TeamMITRE
updated Relationships, Taxonomy_Mappings
2012-05-11CWE Content TeamMITRE
updated Relationships
2017-11-08CWE Content TeamMITRE
updated Taxonomy_Mappings

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Page Last Updated: January 18, 2018