CWE

Common Weakness Enumeration

A Community-Developed List of Software & Hardware Weakness Types

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ID

CWE-1265: Unintended Reentrant Invocation of Non-reentrant Code Via Nested Calls

Weakness ID: 1265
Abstraction: Base
Structure: Simple
Status: Draft
Presentation Filter:
+ Description
During execution of non-reentrant code, the software performs a call that unintentionally produces a nested invocation of the non-reentrant code.
+ Extended Description
In complex software, a single function call may lead to many different possible code paths, some of which may involve deeply nested calls. It may be difficult to foresee all possible code paths that could emanate from a given function call. In some systems, an external actor can manipulate inputs to the system and thereby achieve a wide range of possible control flows. This is frequently of concern in software that executes script from untrusted sources. Examples of such software are web browsers and PDF readers. A weakness is present when one of the possible code paths resulting from a function call alters program state that the original caller assumes to be unchanged during the call.
+ 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)
NatureTypeIDName
ChildOfPillarPillar - a weakness that is the most abstract type of weakness and represents a theme for all class/base/variant weaknesses related to it. A Pillar is different from a Category as a Pillar is still technically a type of weakness that describes a mistake, while a Category represents a common characteristic used to group related things.691Insufficient Control Flow Management
PeerOfBaseBase - a weakness that is still mostly independent of a resource or technology, but with sufficient details to provide specific methods for detection and prevention. Base level weaknesses typically describe issues in terms of 2 or 3 of the following dimensions: behavior, property, technology, language, and resource.663Use of a Non-reentrant Function in a Concurrent Context
CanPrecedeVariantVariant - a weakness that is linked to a certain type of product, typically involving a specific language or technology. More specific than a Base weakness. Variant level weaknesses typically describe issues in terms of 3 to 5 of the following dimensions: behavior, property, technology, language, and resource.416Use After Free
+ Relevant to the view "Software Development" (CWE-699)
NatureTypeIDName
MemberOfCategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic.371State Issues
+ Applicable Platforms
The listings below show possible areas for which the given weakness could appear. These may be for specific named Languages, Operating Systems, Architectures, Paradigms, Technologies, or a class of such platforms. The platform is listed along with how frequently the given weakness appears for that instance.

Languages

Class: Language-Independent (Undetermined Prevalence)

+ 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
Integrity

Technical Impact: Unexpected State

Exploitation of this weakness can leave the application in an unexpected state and cause variables to be reassigned before the first invocation has completed. This may eventually result in memory corruption or unexpected code execution.
Unknown
+ Demonstrative Examples

Example 1

The implementation of the Widget class in the following C++ code is an example of code that is not designed to be reentrant. If an invocation of a method of Widget inadvertently produces a second nested invocation of a method of Widget, then data member backgroundImage may unexpectedly change during execution of the outer call.

(bad code)
Example Language: C++ 
class Widget
{
private:
Image* backgroundImage;

public:
void click()
{
if (backgroundImage)
{
backgroundImage->click();
}
}

void changeBackgroundImage(Image* newImage)
{
if (backgroundImage)
{
delete backgroundImage;
}
backgroundImage = newImage;
}
}

class Image
{
public:
void click()
{
scriptEngine->fireOnImageClick();
/* perform some operations using “this” pointer */
}
}

Looking closer at this example, Widget::click() calls backgroundImage->click(), which in turn calls scriptEngine->fireOnImageClick(). The code within fireOnImageClick() invokes the appropriate script handler routine as defined by the document being rendered. In this scenario this script routine is supplied by an adversary and this malicious script makes a call to Widget::changeBackgroundImage(), deleting the Image object pointed to by backgroundImage. When control returns to Image::click, the function’s "backgroundImage "this" pointer (which is the former value of backgroundImage) is a dangling pointer. The root of this weakness is that while one operation on Widget (click) is in the midst of executing, a second operation on the Widget object may be invoked (in this case, the second invocation is a call to different method, namely changeBackgroundImage) that modifies the non-local variable.

Example 2

This is another example of C++ code that is not designed to be reentrant.

(bad code)
Example Language: C++ 
class Request
{
private:
std::string uri;
/* ... */

public:
void setup(ScriptObject* _uri)
{
this->uri = scriptEngine->coerceToString(_uri);
/* ... */
}

void send(ScriptObject* _data)
{
Credentials credentials = GetCredentials(uri);
std::string data = scriptEngine->coerceToString(_data);
doSend(uri, credentials, data);
}
}

The expected order of operations is a call to Request::setup(), followed by a call to Request::send(). Request::send() calls scriptEngine->coerceToString(_data) to coerce a script-provided parameter into a string. This operation may produce script execution. For example, if the script language is ECMAScript, arbitrary script execution may result if _data is an adversary-supplied ECMAScript object having a custom toString method. If the adversary's script makes a new call to Request::setup, then when control returns to Request::send, the field uri and the local variable credentials will no longer be consistent with one another. As a result, credentials for one resource will be shared improperly with a different resource. The root of this weakness is that while one operation on Request (send) is in the midst of executing, a second operation may be invoked (setup).

+ Observed Examples
ReferenceDescription
In this vulnerability, by registering a malicious onerror handler, an adversary can produce unexpected re-entrance of a CDOMRange object. [REF-1098]
This CVE covers several vulnerable scenarios enabled by abuse of the Class_Terminate feature in Microsoft VBScript. In one scenario, Class_Terminate is used to produce an undesirable re-entrance of ScriptingDictionary during execution of that object’s destructor. In another scenario, a vulnerable condition results from a recursive entrance of a property setter method. This recursive invocation produces a second, spurious call to the Release method of a reference-counted object, causing a UAF when that object is freed prematurely. This vulnerability pattern has been popularized as “Double Kill”. [REF-1099]
+ Potential Mitigations

Phase: Architecture and Design

When architecting a system that will execute untrusted code in response to events, consider executing the untrusted event handlers asynchronously (asynchronous message passing) as opposed to executing them synchronously at the time each event fires. The untrusted code should execute at the start of the next iteration of the thread’s message loop. In this way, calls into non-reentrant code are strictly serialized, so that each operation completes fully before the next operation begins. Special attention must be paid to all places where type coercion may result in script execution. Performing all needed coercions at the very beginning of an operation can help reduce the chance of operations executing at unexpected junctures.

Effectiveness: High

Phase: Implementation

Make sure the code (e.g., function or class) in question is reentrant by not leveraging non-local data, not modifying its own code, and not calling other non-reentrant code.

Effectiveness: High

+ Weakness Ordinalities
OrdinalityDescription
Primary
(where the weakness exists independent of other weaknesses)
+ References
[REF-1098] Jack Tang. "Root Cause Analysis of CVE-2014-1772 – An Internet Explorer Use After Free Vulnerability". 2014-11-05. <https://blog.trendmicro.com/trendlabs-security-intelligence/root-cause-analysis-of-cve-2014-1772-an-internet-explorer-use-after-free-vulnerability/>.
[REF-1099] Simon Zuckerbraun. "It’s Time To Terminate The Terminator". 2018-05-15. <https://www.zerodayinitiative.com/blog/2018/5/15/its-time-to-terminate-the-terminator>.
+ Content History
+ Submissions
Submission DateSubmitterOrganization
2018-12-20Simon ZuckerbraunTrend Micro
+ Modifications
Modification DateModifierOrganization
2020-08-20CWE Content TeamMITRE
updated Demonstrative_Examples, Related_Attack_Patterns
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Page Last Updated: August 20, 2020