CWE-191: Integer Underflow (Wrap or Wraparound)

Code Examples & CVEs

Demonstrative Examples

The following example subtracts from a 32 bit signed integer.

The example has an integer underflow. The value of i is already at the lowest negative value possible, so after subtracting 1, the new value of i is 2147483647.

BadC

#include <stdio.h>#include <stdbool.h>main (void){int i;i = -2147483648;i = i - 1;return 0;}

This code performs a stack allocation based on a length calculation.

Since a and b are declared as signed ints, the "a - b" subtraction gives a negative result (-1). However, since len is declared to be unsigned, len is cast to an extremely large positive number (on 32-bit systems - 4294967295). As a result, the buffer buf[len] declaration uses an extremely large size to allocate on the stack, very likely more than the entire computer's memory space.

BadC

int a = 5, b = 6; 		    size_t len = a - b; 		    char buf[len];    // Just blows up the stack 		   		  }

Observed CVE Examples (4)

CVE-2004-0816

Integer underflow in firewall via malformed packet.

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CVE-2004-1002

Integer underflow by packet with invalid length.

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CVE-2005-0199

Long input causes incorrect length calculation.

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CVE-2005-1891

Malformed icon causes integer underflow in loop counter variable.

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Source-backed guidance

Additional facts reviewed against primary or authoritative security sources.

Detect Integer Underflow (Wrap or Wraparound) with Automated Static Analysis

Documented detection approaches include Automated Static Analysis; recorded impacts include DoS: Crash, Exit, or Restart, DoS: Resource Consumption (CPU), DoS: Resource Consumption (Memory), DoS: Instability, and Modify Memory; observed examples include CVE-2004-0816, CVE-2004-1002, and CVE-2005-0199. Use these source-defined anchors to turn CWE-191 into implementation, review, and verification checks for the affected component.

CWE-191: Integer Underflow (Wrap or Wraparound) — MITRE CWE

Prevent CWE-191 through an SSDF control plan

Use NIST SSDF practices to make prevention of CWE-191, Integer Underflow (Wrap or Wraparound), an explicit development outcome. Translate the CWE definition into security requirements and design constraints, choose safer implementation patterns and toolchain checks, and define acceptance evidence before release. Feed every confirmed occurrence back into the requirements, design review, and coding rules so the same root cause is removed across the product rather than patched in one location.

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

Triage CWE-191 against known exploitation evidence

Use CISA's Known Exploited Vulnerabilities catalog to test whether a vulnerability mapped to CWE-191, Integer Underflow (Wrap or Wraparound), 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-191

Apply MITRE's full root-cause mapping guidance when using CWE-191, Integer Underflow (Wrap or Wraparound). 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-191 with root-cause mapping checks

Apply MITRE's root-cause mapping quick tips to CWE-191, Integer Underflow (Wrap or Wraparound). 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-191: Integer Underflow (Wrap or Wraparound)?+

CWE-191: Integer Underflow (Wrap or Wraparound) is a Common Weakness Enumeration (CWE) entry maintained by MITRE. The product subtracts one value from another, such that the result is less than the minimum allowable integer value, which produces a value that is not equal to the correct result. This can happen in signed and unsigned cases.

What are the security consequences of Integer Underflow (Wrap or Wraparound)?+

If exploited, CWE-191 (Integer Underflow (Wrap or Wraparound)) it can compromise Availability, Integrity, Confidentiality and Access Control, leading to outcomes such as DoS: Crash, Exit, or Restart, DoS: Resource Consumption (CPU), DoS: Resource Consumption (Memory), DoS: Instability, Modify Memory and Execute Unauthorized Code or Commands.

Which programming languages are affected by Integer Underflow (Wrap or Wraparound)?+

CWE-191 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 Integer Underflow (Wrap or Wraparound)?+

MITRE documents real CVEs mapped to CWE-191, including CVE-2004-0816, CVE-2004-1002, CVE-2005-0199 and CVE-2005-1891. 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-191 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-191: Integer Underflow (Wrap or Wraparound)

Extended Description

Technical Details

Applicable To

Security Consequences

Scope

Impact

Scope

Impact

Scope

Impact

Mitigation Strategies

Detection Methods

Code Examples & CVEs

Demonstrative Examples

Observed CVE Examples (4)

CWE Relationships

Parent Weaknesses

Source-backed guidance

Detect Integer Underflow (Wrap or Wraparound) with Automated Static Analysis

Prevent CWE-191 through an SSDF control plan

Triage CWE-191 against known exploitation evidence

Apply precise root-cause mapping to CWE-191

Validate CWE-191 with root-cause mapping checks

Frequently Asked Questions

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