Weakness ID: 415 Vulnerability Mapping:
ALLOWEDThis CWE ID may be used to map to real-world vulnerabilities Abstraction: VariantVariant - 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. |
Description The product calls free() twice on the same memory address, potentially leading to modification of unexpected memory locations. Extended Description When a program calls free() twice with the same argument, the program's memory management data structures become corrupted. This corruption can cause the program to crash or, in some circumstances, cause two later calls to malloc() to return the same pointer. If malloc() returns the same value twice and the program later gives the attacker control over the data that is written into this doubly-allocated memory, the program becomes vulnerable to a buffer overflow attack. Alternate Terms Common Consequences This table 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.Scope | Impact | Likelihood |
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Integrity Confidentiality Availability
| Technical Impact: Modify Memory; Execute Unauthorized Code or Commands Doubly freeing memory may result in a write-what-where condition, allowing an attacker to execute arbitrary code. | |
Potential Mitigations
Phase: Architecture and Design Choose a language that provides automatic memory management. |
Phase: Implementation Ensure that each allocation is freed only once. After freeing a chunk, set the pointer to NULL to ensure the pointer cannot be freed again. In complicated error conditions, be sure that clean-up routines respect the state of allocation properly. If the language is object oriented, ensure that object destructors delete each chunk of memory only once. |
Phase: Implementation Use a static analysis tool to find double free instances. |
Relationships This table 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) Nature | Type | ID | Name |
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ChildOf | Class - a weakness that is described in a very abstract fashion, typically independent of any specific language or technology. More specific than a Pillar Weakness, but more general than a Base Weakness. Class level weaknesses typically describe issues in terms of 1 or 2 of the following dimensions: behavior, property, and resource. | 666 | Operation on Resource in Wrong Phase of Lifetime | ChildOf | Base - 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. | 1341 | Multiple Releases of Same Resource or Handle | ChildOf | Base - 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. | 825 | Expired Pointer Dereference | PeerOf | Base - 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. | 123 | Write-what-where Condition | PeerOf | Variant - 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. | 416 | Use After Free | CanFollow | Base - 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. | 364 | Signal Handler Race Condition |
This table 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 "Weaknesses for Simplified Mapping of Published Vulnerabilities" (CWE-1003) Nature | Type | ID | Name |
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ChildOf | Class - a weakness that is described in a very abstract fashion, typically independent of any specific language or technology. More specific than a Pillar Weakness, but more general than a Base Weakness. Class level weaknesses typically describe issues in terms of 1 or 2 of the following dimensions: behavior, property, and resource. | 672 | Operation on a Resource after Expiration or Release |
This table 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 "CISQ Quality Measures (2020)" (CWE-1305) Nature | Type | ID | Name |
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ChildOf | Class - a weakness that is described in a very abstract fashion, typically independent of any specific language or technology. More specific than a Pillar Weakness, but more general than a Base Weakness. Class level weaknesses typically describe issues in terms of 1 or 2 of the following dimensions: behavior, property, and resource. | 672 | Operation on a Resource after Expiration or Release |
This table 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 "CISQ Data Protection Measures" (CWE-1340) Nature | Type | ID | Name |
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ChildOf | Class - a weakness that is described in a very abstract fashion, typically independent of any specific language or technology. More specific than a Pillar Weakness, but more general than a Base Weakness. Class level weaknesses typically describe issues in terms of 1 or 2 of the following dimensions: behavior, property, and resource. | 672 | Operation on a Resource after Expiration or Release |
Modes Of Introduction The different Modes of Introduction provide information about how and when this weakness may be introduced. The Phase identifies a point in the life cycle at which introduction may occur, while the Note provides a typical scenario related to introduction during the given phase. Likelihood Of Exploit Demonstrative Examples Example 1 The following code shows a simple example of a double free vulnerability. (bad code) Example Language: C
char* ptr = (char*)malloc (SIZE);
...
if (abrt) {
free(ptr);
}
...
free(ptr);
Double free vulnerabilities have two common (and sometimes overlapping) causes:
Although some double free vulnerabilities are not much more complicated than this example, most are spread out across hundreds of lines of code or even different files. Programmers seem particularly susceptible to freeing global variables more than once. Example 2 While contrived, this code should be exploitable on Linux distributions that do not ship with heap-chunk check summing turned on. (bad code) Example Language: C
#include <stdio.h> #include <unistd.h> #define BUFSIZE1 512 #define BUFSIZE2 ((BUFSIZE1/2) - 8)
int main(int argc, char **argv) { char *buf1R1; char *buf2R1; char *buf1R2; buf1R1 = (char *) malloc(BUFSIZE2); buf2R1 = (char *) malloc(BUFSIZE2); free(buf1R1); free(buf2R1); buf1R2 = (char *) malloc(BUFSIZE1); strncpy(buf1R2, argv[1], BUFSIZE1-1); free(buf2R1); free(buf1R2); }
Observed Examples Reference | Description |
| Chain: Signal handler contains too much functionality ( CWE-828), introducing a race condition ( CWE-362) that leads to a double free ( CWE-415). |
| Double free resultant from certain error conditions. |
| Double free resultant from certain error conditions. |
| Double free resultant from certain error conditions. |
| Double free from invalid ASN.1 encoding. |
| Double free from malformed GIF. |
| Double free from malformed GIF. |
| Double free from malformed compressed data. |
Detection Methods
Fuzzing Fuzz testing (fuzzing) is a powerful technique for generating large numbers of diverse inputs - either randomly or algorithmically - and dynamically invoking the code with those inputs. Even with random inputs, it is often capable of generating unexpected results such as crashes, memory corruption, or resource consumption. Fuzzing effectively produces repeatable test cases that clearly indicate bugs, which helps developers to diagnose the issues. |
Automated Static Analysis 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.) |
Affected Resources 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. Vulnerability Mapping Notes Usage: ALLOWED (this CWE ID could be used to map to real-world vulnerabilities) | Reason: Acceptable-Use | Rationale: This CWE entry is at the Variant level of abstraction, which is a preferred level of abstraction for mapping to the root causes of vulnerabilities. | Comments: Carefully read both the name and description to ensure that this mapping is an appropriate fit. Do not try to 'force' a mapping to a lower-level Base/Variant simply to comply with this preferred level of abstraction. |
Notes Relationship This is usually resultant from another weakness, such as an unhandled error or race condition between threads. It could also be primary to weaknesses such as buffer overflows. Theoretical It could be argued that Double Free would be most appropriately located as a child of "Use after Free", but "Use" and "Release" are considered to be distinct operations within vulnerability theory, therefore this is more accurately "Release of a Resource after Expiration or Release", which doesn't exist yet. Taxonomy Mappings Mapped Taxonomy Name | Node ID | Fit | Mapped Node Name |
PLOVER | | | DFREE - Double-Free Vulnerability |
7 Pernicious Kingdoms | | | Double Free |
CLASP | | | Doubly freeing memory |
CERT C Secure Coding | MEM00-C | | Allocate and free memory in the same module, at the same level of abstraction |
CERT C Secure Coding | MEM01-C | | Store a new value in pointers immediately after free() |
CERT C Secure Coding | MEM30-C | CWE More Specific | Do not access freed memory |
CERT C Secure Coding | MEM31-C | | Free dynamically allocated memory exactly once |
Software Fault Patterns | SFP12 | | Faulty Memory Release |
References
[REF-44] Michael Howard, David LeBlanc
and John Viega. "24 Deadly Sins of Software Security". "Sin 8: C++ Catastrophes." Page 143. McGraw-Hill. 2010.
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[REF-62] Mark Dowd, John McDonald
and Justin Schuh. "The Art of Software Security Assessment". Chapter 7, "Double Frees", Page 379. 1st Edition. Addison Wesley. 2006.
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Content History Submissions |
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Submission Date | Submitter | Organization |
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2006-07-19 (CWE Draft 3, 2006-07-19) | PLOVER | | | Modifications |
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Modification Date | Modifier | Organization |
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2008-07-01 | Eric Dalci | Cigital | updated Potential_Mitigations, Time_of_Introduction | 2008-08-01 | | KDM Analytics | added/updated white box definitions | 2008-09-08 | CWE Content Team | MITRE | updated Applicable_Platforms, Common_Consequences, Description, Maintenance_Notes, Relationships, Other_Notes, Relationship_Notes, Taxonomy_Mappings | 2008-11-24 | CWE Content Team | MITRE | updated Relationships, Taxonomy_Mappings | 2009-05-27 | CWE Content Team | MITRE | updated Demonstrative_Examples | 2009-10-29 | CWE Content Team | MITRE | updated Other_Notes | 2010-09-27 | CWE Content Team | MITRE | updated Relationships | 2010-12-13 | CWE Content Team | MITRE | updated Observed_Examples, Relationships | 2011-06-01 | CWE Content Team | MITRE | updated Common_Consequences | 2011-09-13 | CWE Content Team | MITRE | updated Relationships, Taxonomy_Mappings | 2012-05-11 | CWE Content Team | MITRE | updated References, Relationships | 2014-07-30 | CWE Content Team | MITRE | updated Relationships, Taxonomy_Mappings | 2015-12-07 | CWE Content Team | MITRE | updated Relationships | 2017-11-08 | CWE Content Team | MITRE | updated Likelihood_of_Exploit, Relationships, Taxonomy_Mappings, White_Box_Definitions | 2019-01-03 | CWE Content Team | MITRE | updated Relationships | 2019-06-20 | CWE Content Team | MITRE | updated Relationships | 2020-02-24 | CWE Content Team | MITRE | updated References, Relationships | 2020-06-25 | CWE Content Team | MITRE | updated Common_Consequences | 2020-08-20 | CWE Content Team | MITRE | updated Relationships | 2020-12-10 | CWE Content Team | MITRE | updated Relationships | 2021-03-15 | CWE Content Team | MITRE | updated Maintenance_Notes, Theoretical_Notes | 2021-10-28 | CWE Content Team | MITRE | updated Relationships | 2022-04-28 | CWE Content Team | MITRE | updated Demonstrative_Examples, Observed_Examples | 2023-04-27 | CWE Content Team | MITRE | updated Detection_Factors, Relationships, Time_of_Introduction | 2023-06-29 | CWE Content Team | MITRE | updated Mapping_Notes |
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