{"@ID": "122", "@Name": "Heap-based Buffer Overflow", "@Abstraction": "Variant", "@Structure": "Simple", "@Status": "Draft", "Description": "A heap overflow condition is a buffer overflow, where the buffer that can be overwritten is allocated in the heap portion of memory, generally meaning that the buffer was allocated using a routine such as malloc().", "Related_Weaknesses": {"Related_Weakness": [{"@Nature": "ChildOf", "@CWE_ID": "788", "@View_ID": "1000", "@Ordinal": "Primary"}, {"@Nature": "ChildOf", "@CWE_ID": "787", "@View_ID": "1000"}]}, "Weakness_Ordinalities": {"Weakness_Ordinality": {"Ordinality": "Primary"}}, "Applicable_Platforms": {"Language": [{"@Class": "Memory-Unsafe", "@Prevalence": "Often"}, {"@Name": "C", "@Prevalence": "Often"}, {"@Name": "C++", "@Prevalence": "Often"}], "Technology": {"@Class": "Not Technology-Specific", "@Prevalence": "Undetermined"}}, "Alternate_Terms": {"Alternate_Term": [{"Term": "Heap Overflow"}, {"Term": "Heap Buffer Overflow"}]}, "Modes_Of_Introduction": {"Introduction": {"Phase": "Implementation"}}, "Likelihood_Of_Exploit": "High", "Common_Consequences": {"Consequence": [{"Scope": "Availability", "Impact": ["DoS: Crash, Exit, or Restart", "DoS: Resource Consumption (CPU)", "DoS: Resource Consumption (Memory)"], "Note": "Buffer overflows generally lead to crashes. Other attacks leading to lack of availability are possible, including putting the program into an infinite loop."}, {"Scope": ["Integrity", "Confidentiality", "Availability", "Access Control"], "Impact": ["Execute Unauthorized Code or Commands", "Bypass Protection Mechanism", "Modify Memory"], "Note": "Buffer overflows often can be used to execute arbitrary code, which is usually outside the scope of a program's implicit security policy. Besides important user data, heap-based overflows can be used to overwrite function pointers that may be living in memory, pointing it to the attacker's code. Even in applications that do not explicitly use function pointers, the run-time will usually leave many in memory. For example, object methods in C++ are generally implemented using function pointers. Even in C programs, there is often a global offset table used by the underlying runtime."}, {"Scope": ["Integrity", "Confidentiality", "Availability", "Access Control", "Other"], "Impact": ["Execute Unauthorized Code or Commands", "Bypass Protection Mechanism", "Other"], "Note": "When the consequence is arbitrary code execution, this can often be used to subvert any other security service."}]}, "Detection_Methods": {"Detection_Method": [{"@Detection_Method_ID": "DM-13", "Method": "Fuzzing", "Description": "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.", "Effectiveness": "High"}, {"@Detection_Method_ID": "DM-15", "Method": "Automated Dynamic Analysis", "Description": "Use tools that are integrated during\n\t     compilation to insert runtime error-checking mechanisms\n\t     related to memory safety errors, such as AddressSanitizer\n\t     (ASan) for C/C++ [REF-1518].", "Effectiveness": "Moderate", "Effectiveness_Notes": "Crafted inputs are necessary to\n\t     reach the code containing the error, such as generated\n\t     by fuzzers.  Also, these tools may reduce performance,\n\t     and they only report the error condition - not the\n\t     original mistake that led to the\n\t     error."}]}, "Potential_Mitigations": {"Mitigation": [{"Description": "Pre-design: Use a language or compiler that performs automatic bounds checking."}, {"Phase": "Architecture and Design", "Description": "Use an abstraction library to abstract away risky APIs. Not a complete solution."}, {"@Mitigation_ID": "MIT-10", "Phase": ["Operation", "Build and Compilation"], "Strategy": "Environment Hardening", "Description": {"xhtml:p": ["Use automatic buffer overflow detection mechanisms that are offered by certain compilers or compiler extensions. Examples include: the Microsoft Visual Studio /GS flag, Fedora/Red Hat FORTIFY_SOURCE GCC flag, StackGuard, and ProPolice, which provide various mechanisms including canary-based detection and range/index checking.", "D3-SFCV (Stack Frame Canary Validation) from D3FEND [REF-1334] discusses canary-based detection in detail."]}, "Effectiveness": "Defense in Depth", "Effectiveness_Notes": {"xhtml:p": "This is not necessarily a complete solution, since these mechanisms only detect certain types of overflows. In addition, the result is still a denial of service, since the typical response is to exit the application."}}, {"@Mitigation_ID": "MIT-11", "Phase": ["Operation", "Build and Compilation"], "Strategy": "Environment Hardening", "Description": {"xhtml:p": ["Run or compile the software using features or extensions that randomly arrange the positions of a program's executable and libraries in memory. Because this makes the addresses unpredictable, it can prevent an attacker from reliably jumping to exploitable code.", "Examples include Address Space Layout Randomization (ASLR) [REF-58] [REF-60] and Position-Independent Executables (PIE) [REF-64]. Imported modules may be similarly realigned if their default memory addresses conflict with other modules, in a process known as \"rebasing\" (for Windows) and \"prelinking\" (for Linux) [REF-1332] using randomly generated addresses. ASLR for libraries cannot be used in conjunction with prelink since it would require relocating the libraries at run-time, defeating the whole purpose of prelinking.", "For more information on these techniques see D3-SAOR (Segment Address Offset Randomization) from D3FEND [REF-1335]."]}, "Effectiveness": "Defense in Depth", "Effectiveness_Notes": "These techniques do not provide a complete solution.  For instance, exploits frequently use a bug that discloses memory addresses in order to maximize reliability of code execution [REF-1337]. It has also been shown that a side-channel attack can bypass ASLR [REF-1333]."}, {"Phase": "Implementation", "Description": "Implement and perform bounds checking on input."}, {"Phase": "Implementation", "Strategy": "Libraries or Frameworks", "Description": "Do not use dangerous functions such as gets. Look for their safe equivalent, which checks for the boundary."}, {"Phase": "Operation", "Description": "Use OS-level preventative functionality. This is not a complete solution, but it provides some defense in depth."}]}, "Demonstrative_Examples": {"Demonstrative_Example": [{"Intro_Text": "While buffer overflow examples can be rather complex, it is possible to have very simple, yet still exploitable, heap-based buffer overflows:", "Example_Code": {"@Nature": "Bad", "@Language": "C", "xhtml:div": {"xhtml:br": null, "xhtml:div": {"@style": "margin-left:1em;", "xhtml:br": [null, null], "#text": "char *buf;buf = (char *)malloc(sizeof(char)*BUFSIZE);strcpy(buf, argv[1]);"}, "#text": "#define BUFSIZE 256int main(int argc, char **argv) {}"}}, "Body_Text": "The buffer is allocated heap memory with a fixed size, but there is no guarantee the string in argv[1] will not exceed this size and cause an overflow."}, {"@Demonstrative_Example_ID": "DX-19", "Intro_Text": "This example applies an encoding procedure to an input string and stores it into a buffer.", "Example_Code": {"@Nature": "Bad", "@Language": "C", "xhtml:div": {"xhtml:div": {"@style": "margin-left:1em;", "xhtml:div": {"xhtml:br": [null, null, null, null, null], "xhtml:div": [{"@style": "margin-left:1em;", "#text": "die(\"user string too long, die evil hacker!\");"}, {"@style": "margin-left:1em;", "xhtml:div": {"xhtml:div": [{"@style": "margin-left:1em;", "xhtml:br": [null, null, null, null], "#text": "dst_buf[dst_index++] = '&';dst_buf[dst_index++] = 'a';dst_buf[dst_index++] = 'm';dst_buf[dst_index++] = 'p';dst_buf[dst_index++] = ';';"}, {"@style": "margin-left:1em;", "xhtml:div": {"xhtml:br": [null, null], "xhtml:i": "/* encode to &lt; */"}}], "xhtml:br": [null, null], "#text": "if( '&' == user_supplied_string[i] ){}else if ('<' == user_supplied_string[i] ){}else dst_buf[dst_index++] = user_supplied_string[i];"}}], "#text": "int i, dst_index;char *dst_buf = (char*)malloc(4*sizeof(char) * MAX_SIZE);if ( MAX_SIZE <= strlen(user_supplied_string) ){}dst_index = 0;for ( i = 0; i < strlen(user_supplied_string); i++ ){}return dst_buf;"}}, "#text": "char * copy_input(char *user_supplied_string){}"}}, "Body_Text": "The programmer attempts to encode the ampersand character in the user-controlled string, however the length of the string is validated before the encoding procedure is applied. Furthermore, the programmer assumes encoding expansion will only expand a given character by a factor of 4, while the encoding of the ampersand expands by 5. As a result, when the encoding procedure expands the string it is possible to overflow the destination buffer if the attacker provides a string of many ampersands."}]}, "Observed_Examples": {"Observed_Example": [{"Reference": "CVE-2025-46687", "Description": "Chain: Javascript engine code does not perform a length check (CWE-1284) leading to integer overflow (CWE-190) causing allocation of smaller buffer than expected (CWE-131) resulting in a heap-based buffer overflow (CWE-122)", "Link": "https://www.cve.org/CVERecord?id=CVE-2025-46687"}, {"Reference": "CVE-2021-43537", "Description": "Chain: in a web browser, an unsigned 64-bit integer is forcibly cast to a 32-bit integer (CWE-681) and potentially leading to an integer overflow (CWE-190). If an integer overflow occurs, this can cause heap memory corruption (CWE-122)", "Link": "https://www.cve.org/CVERecord?id=CVE-2021-43537"}, {"Reference": "CVE-2007-4268", "Description": "Chain: integer signedness error (CWE-195) passes signed comparison, leading to heap overflow (CWE-122)", "Link": "https://www.cve.org/CVERecord?id=CVE-2007-4268"}, {"Reference": "CVE-2009-2523", "Description": "Chain: product does not handle when an input string is not NULL terminated (CWE-170), leading to buffer over-read (CWE-125) or heap-based buffer overflow (CWE-122).", "Link": "https://www.cve.org/CVERecord?id=CVE-2009-2523"}, {"Reference": "CVE-2021-29529", "Description": "Chain: machine-learning product can have a heap-based\n\t      buffer overflow (CWE-122) when some integer-oriented bounds are\n\t      calculated by using ceiling() and floor() on floating point values\n\t      (CWE-1339)", "Link": "https://www.cve.org/CVERecord?id=CVE-2021-29529"}, {"Reference": "CVE-2010-1866", "Description": "Chain: integer overflow (CWE-190) causes a negative signed value, which later bypasses a maximum-only check (CWE-839), leading to heap-based buffer overflow (CWE-122).", "Link": "https://www.cve.org/CVERecord?id=CVE-2010-1866"}]}, "Functional_Areas": {"Functional_Area": "Memory Management"}, "Affected_Resources": {"Affected_Resource": "Memory"}, "Taxonomy_Mappings": {"Taxonomy_Mapping": [{"@Taxonomy_Name": "CLASP", "Entry_Name": "Heap overflow"}, {"@Taxonomy_Name": "Software Fault Patterns", "Entry_ID": "SFP8", "Entry_Name": "Faulty Buffer Access"}, {"@Taxonomy_Name": "CERT C Secure Coding", "Entry_ID": "STR31-C", "Entry_Name": "Guarantee that storage for strings has sufficient space for character data and the null terminator", "Mapping_Fit": "CWE More Specific"}, {"@Taxonomy_Name": "ISA/IEC 62443", "Entry_ID": "Part 4-2", "Entry_Name": "Req CR 3.5"}, {"@Taxonomy_Name": "ISA/IEC 62443", "Entry_ID": "Part 3-3", "Entry_Name": "Req SR 3.5"}, {"@Taxonomy_Name": "ISA/IEC 62443", "Entry_ID": "Part 4-1", "Entry_Name": "Req SI-1"}, {"@Taxonomy_Name": "ISA/IEC 62443", "Entry_ID": "Part 4-1", "Entry_Name": "Req SI-2"}, {"@Taxonomy_Name": "ISA/IEC 62443", "Entry_ID": "Part 4-1", "Entry_Name": "Req SVV-1"}, {"@Taxonomy_Name": "ISA/IEC 62443", "Entry_ID": "Part 4-1", "Entry_Name": "Req SVV-3"}]}, "Related_Attack_Patterns": {"Related_Attack_Pattern": {"@CAPEC_ID": "92"}}, "References": {"Reference": [{"@External_Reference_ID": "REF-7", "@Section": "Chapter 5, \"Heap Overruns\" Page 138"}, {"@External_Reference_ID": "REF-44", "@Section": "\"Sin 5: Buffer Overruns.\" Page 89"}, {"@External_Reference_ID": "REF-62", "@Section": "Chapter 3, \"Nonexecutable Stack\", Page 76"}, {"@External_Reference_ID": "REF-62", "@Section": "Chapter 5, \"Protection Mechanisms\", Page 189"}, {"@External_Reference_ID": "REF-58"}, {"@External_Reference_ID": "REF-60"}, {"@External_Reference_ID": "REF-64"}, {"@External_Reference_ID": "REF-18"}, {"@External_Reference_ID": "REF-1337", "@Section": "Memory information leaks"}, {"@External_Reference_ID": "REF-1332"}, {"@External_Reference_ID": "REF-1333"}, {"@External_Reference_ID": "REF-1334"}, {"@External_Reference_ID": "REF-1335"}, {"@External_Reference_ID": "REF-1477"}, {"@External_Reference_ID": "REF-1518"}]}, "Mapping_Notes": {"Usage": "Allowed", "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.", "Reasons": {"Reason": {"@Type": "Acceptable-Use"}}}, "Notes": {"Note": {"@Type": "Terminology", "#text": "There is significant inconsistency\n\t   regarding the \"buffer overflow\" term, which can have\n\t   multiple interpretations and uses. Many people mean\n\t   \"writing past the end of a buffer.\"  Others mean \"writing\n\t   past the end of a buffer, or before the beginning of a\n\t   buffer.\"  Still others might include \"read\" in the term."}}, "Content_History": {"Submission": {"Submission_Name": "CLASP", "Submission_Date": "2006-07-19", "Submission_Version": "Draft 3", "Submission_ReleaseDate": "2006-07-19"}, "Modification": [{"Modification_Name": "Eric Dalci", "Modification_Organization": "Cigital", "Modification_Date": "2008-07-01", "Modification_Version": "1.0", "Modification_ReleaseDate": "2008-09-09", "Modification_Comment": "updated Potential_Mitigations, Time_of_Introduction"}, {"Modification_Organization": "KDM Analytics", "Modification_Date": "2008-08-01", "Modification_Version": "1.0", "Modification_ReleaseDate": "2008-09-09", "Modification_Comment": "added/updated white box definitions"}, {"Modification_Name": "CWE Content Team", "Modification_Organization": "MITRE", "Modification_Date": "2008-09-08", "Modification_Version": "1.0", "Modification_ReleaseDate": "2008-09-09", "Modification_Comment": "updated Applicable_Platforms, Common_Consequences, Relationships, Other_Notes, Taxonomy_Mappings, Weakness_Ordinalities"}, {"Modification_Name": "CWE Content Team", "Modification_Organization": "MITRE", "Modification_Date": "2008-11-24", "Modification_Version": "1.1", "Modification_ReleaseDate": "2008-11-25", "Modification_Comment": "updated Common_Consequences, Other_Notes, Relationship_Notes"}, {"Modification_Name": "CWE Content Team", "Modification_Organization": "MITRE", "Modification_Date": "2009-01-12", "Modification_Version": "1.2", "Modification_ReleaseDate": "2009-01-12", "Modification_Comment": "updated Common_Consequences, Relationships"}, {"Modification_Name": "CWE Content Team", "Modification_Organization": "MITRE", "Modification_Date": "2009-10-29", "Modification_Version": "1.6", "Modification_ReleaseDate": "2009-10-29", "Modification_Comment": "updated Relationships"}, {"Modification_Name": "CWE Content Team", "Modification_Organization": "MITRE", "Modification_Date": "2010-02-16", "Modification_Version": "1.8", "Modification_ReleaseDate": "2010-02-16", "Modification_Comment": "updated References"}, {"Modification_Name": "CWE Content Team", "Modification_Organization": "MITRE", "Modification_Date": "2011-06-01", "Modification_Version": "1.13", "Modification_ReleaseDate": "2011-06-01", "Modification_Comment": "updated Common_Consequences"}, {"Modification_Name": "CWE Content Team", "Modification_Organization": "MITRE", "Modification_Date": "2012-05-11", "Modification_Version": "2.2", "Modification_ReleaseDate": "2012-05-15", "Modification_Comment": "updated Demonstrative_Examples, References, Relationships"}, {"Modification_Name": "CWE Content Team", "Modification_Organization": "MITRE", "Modification_Date": "2012-10-30", "Modification_Version": "2.3", "Modification_ReleaseDate": "2012-10-30", "Modification_Comment": "updated Demonstrative_Examples"}, {"Modification_Name": "CWE Content Team", "Modification_Organization": "MITRE", "Modification_Date": "2013-02-21", "Modification_Version": "2.4", "Modification_ReleaseDate": "2013-02-21", "Modification_Comment": "updated Demonstrative_Examples, Potential_Mitigations"}, {"Modification_Name": "CWE Content Team", "Modification_Organization": "MITRE", "Modification_Date": "2014-06-23", "Modification_Version": "2.7", "Modification_ReleaseDate": "2014-06-23", "Modification_Comment": "updated Observed_Examples"}, {"Modification_Name": "CWE Content Team", "Modification_Organization": "MITRE", "Modification_Date": "2014-07-30", "Modification_Version": "2.8", "Modification_ReleaseDate": "2014-07-31", "Modification_Comment": "updated Relationships, Taxonomy_Mappings"}, {"Modification_Name": "CWE Content Team", "Modification_Organization": "MITRE", "Modification_Date": "2017-11-08", "Modification_Version": "3.0", "Modification_ReleaseDate": "2017-11-08", "Modification_Comment": "updated Causal_Nature, Likelihood_of_Exploit, Observed_Examples, References, Relationships, Taxonomy_Mappings, White_Box_Definitions"}, {"Modification_Name": "CWE Content Team", "Modification_Organization": "MITRE", "Modification_Date": "2018-03-27", "Modification_Version": "3.1", "Modification_ReleaseDate": "2018-03-27", "Modification_Comment": "updated References"}, {"Modification_Name": "CWE Content Team", "Modification_Organization": "MITRE", "Modification_Date": "2019-01-03", "Modification_Version": "3.2", "Modification_ReleaseDate": "2019-01-03", "Modification_Comment": "updated Relationships"}, {"Modification_Name": "CWE Content Team", "Modification_Organization": "MITRE", "Modification_Date": "2020-02-24", "Modification_Version": "4.0", "Modification_ReleaseDate": "2020-02-24", "Modification_Comment": "updated Relationships"}, {"Modification_Name": "CWE Content Team", "Modification_Organization": "MITRE", "Modification_Date": "2021-03-15", "Modification_Version": "4.4", "Modification_ReleaseDate": "2021-03-15", "Modification_Comment": "updated References"}, {"Modification_Name": "CWE Content Team", "Modification_Organization": "MITRE", "Modification_Date": "2021-07-20", "Modification_Version": "4.5", "Modification_ReleaseDate": "2021-07-20", "Modification_Comment": "updated Observed_Examples"}, {"Modification_Name": "CWE Content Team", "Modification_Organization": "MITRE", "Modification_Date": "2023-04-27", "Modification_Version": "4.11", "Modification_ReleaseDate": "2023-04-27", "Modification_Comment": "updated Detection_Factors, Potential_Mitigations, References, Relationships, Time_of_Introduction"}, {"Modification_Name": "CWE Content Team", "Modification_Organization": "MITRE", "Modification_Date": "2023-06-29", "Modification_Version": "4.12", "Modification_ReleaseDate": "2023-06-29", "Modification_Comment": "updated Mapping_Notes"}, {"Modification_Name": "CWE Content Team", "Modification_Organization": "MITRE", "Modification_Date": "2023-10-26", "Modification_Version": "4.13", "Modification_ReleaseDate": "2023-10-26", "Modification_Comment": "updated Observed_Examples"}, {"Modification_Name": "CWE Content Team", "Modification_Organization": "MITRE", "Modification_Date": "2024-02-29", "Modification_Version": "4.14", "Modification_ReleaseDate": "2024-02-29", "Modification_Comment": "updated Observed_Examples, Taxonomy_Mappings"}, {"Modification_Name": "CWE Content Team", "Modification_Organization": "MITRE", "Modification_Date": "2025-04-03", "Modification_Version": "4.17", "Modification_ReleaseDate": "2025-04-03", "Modification_Comment": "updated Applicable_Platforms"}, {"Modification_Name": "CWE Content Team", "Modification_Organization": "MITRE", "Modification_Date": "2025-09-09", "Modification_Version": "4.18", "Modification_ReleaseDate": "2025-09-09", "Modification_Comment": "updated Functional_Areas, References"}, {"Modification_Name": "CWE Content Team", "Modification_Organization": "MITRE", "Modification_Date": "2025-12-11", "Modification_Version": "4.19", "Modification_ReleaseDate": "2025-12-11", "Modification_Comment": "updated Alternate_Terms, Applicable_Platforms, Detection_Factors, Observed_Examples, References, Relationship_Notes, Terminology_Notes"}, {"Modification_Name": "CWE Content Team", "Modification_Organization": "MITRE", "Modification_Date": "2026-01-21", "Modification_Version": "4.19.1", "Modification_ReleaseDate": "2026-01-21", "Modification_Comment": "updated Relationships"}], "Contribution": {"@Type": "Content", "Contribution_Name": "participants in the CWE ICS/OT SIG 62443 Mapping Fall Workshop", "Contribution_Date": "2023-11-14", "Contribution_Version": "4.14", "Contribution_ReleaseDate": "2024-02-29", "Contribution_Comment": "Contributed or reviewed taxonomy mappings for ISA/IEC 62443"}}}