CWE-415: Double Free

Code Examples & CVEs

Demonstrative Examples

The following code shows a simple example of a double free vulnerability.

Double free vulnerabilities have two common (and sometimes overlapping) causes:

BadC

char* ptr = (char*)malloc (SIZE); 				   ... 				   if (abrt) { 				    					 free(ptr); 				    				   } 				   ... 				   free(ptr);

While contrived, this code should be exploitable on Linux distributions that do not ship with heap-chunk check summing turned on.

BadC

#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 CVE Examples (8)

CVE-2006-5051

Chain: Signal handler contains too much functionality (CWE-828), introducing a race condition (CWE-362) that leads to a double free (CWE-415).

View Details

CVE-2004-0642

Double free resultant from certain error conditions.

View Details

CVE-2004-0772

Double free resultant from certain error conditions.

View Details

CVE-2005-1689

Double free resultant from certain error conditions.

View Details

CVE-2003-0545

Double free from invalid ASN.1 encoding.

View Details

CVE-2003-1048

Double free from malformed GIF.

View Details

CVE-2005-0891

Double free from malformed GIF.

View Details

CVE-2002-0059

Double free from malformed compressed data.

View Details

Source-backed guidance

Additional facts reviewed against primary or authoritative security sources.

Verify controls for CWE-415 with SSDF evidence

Use NIST SSDF verification and vulnerability-response practices to detect CWE-415, Double Free, throughout the product lifecycle. Derive review questions, static or dynamic checks, and negative tests from the CWE's causal behavior; define the components and lifecycle stages each check covers; and retain findings with enough evidence to distinguish the root cause from symptoms and impacts. Track escapes and false negatives, then improve the verification plan after every confirmed occurrence.

NIST SP 800-218 Secure Software Development Framework — National Institute of Standards and Technology

Address Double Free during Architecture and Design

MITRE associates mitigation with Architecture and Design, and Implementation; documented detection approaches include Fuzzing, Automated Static Analysis, and Automated Dynamic Analysis; recorded impacts include Modify Memory, and Execute Unauthorized Code or Commands. Use these source-defined anchors to turn CWE-415 into implementation, review, and verification checks for the affected component.

CWE-415: Double Free — MITRE CWE

Triage CWE-415 against known exploitation evidence

Use CISA's Known Exploited Vulnerabilities catalog to test whether a vulnerability mapped to CWE-415, Double Free, has evidence of exploitation in the wild. Confirm the CVE-to-CWE root-cause mapping independently before attaching the example, then capture the affected product, required action, and remediation deadline. A missing KEV match is not evidence that the weakness is unexploited, and a KEV entry must not be generalized to every occurrence of this CWE.

Known Exploited Vulnerabilities Catalog — Cybersecurity and Infrastructure Security Agency

Apply precise root-cause mapping to CWE-415

Apply MITRE's full root-cause mapping guidance when using CWE-415, Double Free. Separate weakness language from attacker prerequisites and technical impact, check the entry's abstraction and vulnerability-mapping notes, and prefer the most specific Base or Variant supported by the evidence. Record the rejected alternatives and require an independent review before the mapping is used for remediation trends or program metrics.

CVE to CWE Root Cause Mapping Guidance — MITRE CWE

Validate CWE-415 with root-cause mapping checks

Apply MITRE's root-cause mapping quick tips to CWE-415, Double Free. Confirm the finding describes the causal weakness rather than an impact or attack pattern, compare the abstraction and mapping notes with plausible alternatives, and have a second reviewer challenge the selection. Preserve the evidence and reasoning so recurring defects can be measured against one consistent identifier.

CVE to CWE Root Cause Mapping Quick Tips — MITRE CWE

Frequently Asked Questions

What is CWE-415: Double Free?+

CWE-415: Double Free is a Common Weakness Enumeration (CWE) entry maintained by MITRE. The product calls free() twice on the same memory address.

What are the security consequences of Double Free?+

If exploited, CWE-415 (Double Free) it can compromise Integrity, Confidentiality and Availability, leading to outcomes such as Modify Memory and Execute Unauthorized Code or Commands.

How do you prevent or mitigate Double Free?+

Recommended mitigations for CWE-415 include: Choose a language that provides automatic memory management. 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. Use a static analysis tool to find double free instances.

Which programming languages are affected by Double Free?+

CWE-415 commonly affects C, C++ and Memory-Unsafe. Note that weaknesses are often language-agnostic patterns, so secure coding practices apply broadly.

What are real-world examples of Double Free?+

MITRE documents real CVEs mapped to CWE-415, including CVE-2006-5051, CVE-2004-0642, CVE-2004-0772, CVE-2005-1689 and CVE-2003-0545. You can look up the full details of each CVE, including CVSS scores and remediation guidance, on our CVE Lookup tool.

What is the difference between a CWE and a CVE?+

A CWE (Common Weakness Enumeration) like CWE-415 describes a category of software weakness — the underlying flaw type. A CVE (Common Vulnerabilities and Exposures) identifies a specific, real-world vulnerability in a particular product. In short, a CWE is the kind of mistake, and a CVE is an instance of that mistake being found in software.

CWE-415: Double Free

Technical Details

Applicable To

Security Consequences

Scope

Impact

Mitigation Strategies

Phase

Description

Phase

Description

Phase

Description

Detection Methods

Code Examples & CVEs

Demonstrative Examples

Observed CVE Examples (8)

CWE Relationships

Parent Weaknesses

Source-backed guidance

Verify controls for CWE-415 with SSDF evidence

Address Double Free during Architecture and Design

Triage CWE-415 against known exploitation evidence

Apply precise root-cause mapping to CWE-415

Validate CWE-415 with root-cause mapping checks

Frequently Asked Questions

Learn More