CWE-197: Numeric Truncation Error

Extended Description

When a primitive is cast to a smaller primitive, the high order bits of the large value are lost in the conversion, potentially resulting in an unexpected value that is not equal to the original value. This value may be required as an index into a buffer, a loop iterator, or simply necessary state data. In any case, the value cannot be trusted and the system will be in an undefined state. While this method may be employed viably to isolate the low bits of a value, this usage is rare, and truncation usually implies that an implementation error has occurred.

Code Examples & CVEs

Demonstrative Examples

This example, while not exploitable, shows the possible mangling of values associated with truncation errors:

The above code, when compiled and run on certain systems, returns the following output:

BadC

int intPrimitive;short shortPrimitive;intPrimitive = (int)(~((int)0) ^ (1 << (sizeof(int)*8-1)));shortPrimitive = intPrimitive;printf("Int MAXINT: %d\nShort MAXINT: %d\n", intPrimitive, shortPrimitive);

In the following Java example, the method updateSalesForProduct is part of a business application class that updates the sales information for a particular product. The method receives as arguments the product ID and the integer amount sold. The product ID is used to retrieve the total product count from an inventory object which returns the count as an integer. Before calling the method of the sales object to update the sales count the integer values are converted to The primitive type short since the method requires short type for the method arguments.

However, a numeric truncation error can occur if the integer values are higher than the maximum value allowed for the primitive type short. This can cause unexpected results or loss or corruption of data. In this case the sales database may be corrupted with incorrect data. Explicit casting from a from a larger size primitive type to a smaller size primitive type should be prevented. The following example an if statement is added to validate that the integer values less than the maximum value for the primitive type short before the explicit cast and the call to the sales method.

BadJava

...                      // update sales database for number of product sold with product ID                      public void updateSalesForProduct(String productID, int amountSold) {                                                                                 // get the total number of products in inventory database                            int productCount = inventory.getProductCount(productID);                            // convert integer values to short, the method for the                                                                                    // sales object requires the parameters to be of type short                            short count = (short) productCount;short sold = (short) amountSold;                            // update sales database for product                            sales.updateSalesCount(productID, count, sold);                      }...

GoodJava

...                      // update sales database for number of product sold with product ID                      public void updateSalesForProduct(String productID, int amountSold) {                                                                                 // get the total number of products in inventory database                            int productCount = inventory.getProductCount(productID);                            // make sure that integer numbers are not greater than                                                                                    // maximum value for type short before converting                            if ((productCount < Short.MAX_VALUE) && (amountSold < Short.MAX_VALUE)) {                                                                                                   // convert integer values to short, the method for the                                                                                                      // sales object requires the parameters to be of type short                                  short count = (short) productCount;short sold = (short) amountSold;                                  // update sales database for product                                  sales.updateSalesCount(productID, count, sold);                                                        else {                            // throw exception or perform other processing                                                        ...}                      }...

Observed CVE Examples (3)

CVE-2020-17087

Chain: integer truncation (CWE-197) causes small buffer allocation (CWE-131) leading to out-of-bounds write (CWE-787) in kernel pool, as exploited in the wild per CISA KEV.

View Details

CVE-2009-0231

Integer truncation of length value leads to heap-based buffer overflow.

View Details

CVE-2008-3282

Size of a particular type changes for 64-bit platforms, leading to an integer truncation in document processor causes incorrect index to be generated.

View Details

Source-backed guidance

Additional facts reviewed against primary or authoritative security sources.

Verify controls for CWE-197 with SSDF evidence

Use NIST SSDF verification and vulnerability-response practices to detect CWE-197, Numeric Truncation Error, 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 Numeric Truncation Error during Implementation

MITRE associates mitigation with Implementation; documented detection approaches include Fuzzing, and Automated Static Analysis; recorded impacts include Modify Memory. Use these source-defined anchors to turn CWE-197 into implementation, review, and verification checks for the affected component.

CWE-197: Numeric Truncation Error — MITRE CWE

Triage CWE-197 against known exploitation evidence

Use CISA's Known Exploited Vulnerabilities catalog to test whether a vulnerability mapped to CWE-197, Numeric Truncation Error, 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-197

Apply MITRE's full root-cause mapping guidance when using CWE-197, Numeric Truncation Error. 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-197 with root-cause mapping checks

Apply MITRE's root-cause mapping quick tips to CWE-197, Numeric Truncation Error. 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-197: Numeric Truncation Error?+

CWE-197: Numeric Truncation Error is a Common Weakness Enumeration (CWE) entry maintained by MITRE. Truncation errors occur when a primitive is cast to a primitive of a smaller size and data is lost in the conversion. When a primitive is cast to a smaller primitive, the high order bits of the large value are lost in the conversion, potentially resulting in an unexpected value that is not equal to the original value. This value may be required as an index into a buffer, a loop iterator, or simply necessary state data. In any case, the value cannot be trusted and the system will be in an undefined state. While this method may be employed viably to isolate the low bits of a value, this usage is rare, and truncation usually implies that an implementation error has occurred.

What are the security consequences of Numeric Truncation Error?+

If exploited, CWE-197 (Numeric Truncation Error) it can compromise Integrity, leading to outcomes such as Modify Memory.

How do you prevent or mitigate Numeric Truncation Error?+

Recommended mitigations for CWE-197 include: Ensure that no casts, implicit or explicit, take place that move from a larger size primitive or a smaller size primitive.

Which programming languages are affected by Numeric Truncation Error?+

CWE-197 commonly affects C, C++, Java and C#. Note that weaknesses are often language-agnostic patterns, so secure coding practices apply broadly.

What are real-world examples of Numeric Truncation Error?+

MITRE documents real CVEs mapped to CWE-197, including CVE-2020-17087, CVE-2009-0231 and CVE-2008-3282. 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-197 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-197: Numeric Truncation Error

Extended Description

Technical Details

Applicable To

Security Consequences

Scope

Impact

Mitigation Strategies

Phase

Description

Detection Methods

Code Examples & CVEs

Demonstrative Examples

Observed CVE Examples (3)

CWE Relationships

Parent Weaknesses

Source-backed guidance

Verify controls for CWE-197 with SSDF evidence

Address Numeric Truncation Error during Implementation

Triage CWE-197 against known exploitation evidence

Apply precise root-cause mapping to CWE-197

Validate CWE-197 with root-cause mapping checks

Frequently Asked Questions

Learn More