CWE/SANS TOP 25 Most Dangerous Software Errors

What Errors Are Included in the Top 25 Software Errors?

    Click on the CWE ID in any of the listings in the chart below and you will be directed to the relevant spot in the MITRE CWE site where you will find the following:

    • Ranking of each Top 25 entry,
    • Links to the full CWE entry data,
    • Data fields for weakness prevalence and consequences,
    • Remediation cost,
    • Ease of detection,
    • Code examples,
    • Detection Methods,
    • Attack frequency and attacker awareness
    • Related CWE entries, and
    • Related patterns of attack for this weakness.

    Each entry at the Top 25 Software Errors site also includes fairly extensive prevention and remediation steps that developers can take to mitigate or eliminate the weakness.

    The CWE Top 25

    1CWE-787Out-of-bounds Write
    2CWE-79Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
    3CWE-125Out-of-bounds Read
    4CWE-20Improper Input Validation
    5CWE-78Improper Neutralization of Special Elements used in an OS Command ('OS Command Injection')
    6CWE-89Improper Neutralization of Special Elements used in an SQL Command ('SQL Injection')
    7CWE-416Use After Free
    8CWE-22Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal')
    9CWE-352Cross-Site Request Forgery (CSRF)
    10CWE-434Unrestricted Upload of File with Dangerous Type

    Missing Authentication for Critical Function

    12CWE-190Integer Overflow or Wraparound
    13CWE-502Deserialization of Untrusted Data
    14CWE-287Improper Authentication
    15CWE-476NULL Pointer Dereference
    16CWE-798Use of Hard-coded Credentials
    17CWE-119Improper Restriction of Operations within the Bounds of a Memory Buffer
    18CWE-862Missing Authorization
    19CWE-276Incorrect Default Permissions
    20CWE-200Exposure of Sensitive Information to an Unauthorized Actor
    21CWE-522Insufficiently Protected Credentials
    22CWE-732Incorrect Permission Assignment for Critical Resource
    23CWE-611Improper Restriction of XML External Entity Reference
    24CWE-918Server-Side Request Forgery (SSRF)
    25CWE-77Improper Neutralization of Special Elements used in a Command ('Command Injection')

    Resources to Help Eliminate The Top 25 Software Errors

    1. SANS Application Security Courses

      The SANS Cloud Security curriculum seeks to ingrain security into the minds of every developer in the world by providing world-class educational resources to design, develop, procure, deploy, and manage secure software. The SANS cloud security and DevSecOps faculty are real-world practitioners with decades of application security experience. The concepts covered in our courses will be applicable to your software security program the day you return to work:

      SANS maintains an Application Security CyberTalent Assessment that measures secure coding skills and allow programmers to determine gaps in their knowledge of secure coding and allows buyers to ensure outsourced programmers have sufficient programming skills. Organizations can learn more at

    2. Developer Security Awareness Training

      The SANS Security Awareness Developer product provides pinpoint software security awareness training on demand, all from the comfort of your desk. Application security awareness training includes over 30+ modules averaging 7-10 minutes in length to maximize learner engagement and retention. The modules cover the full breadth and depth of topics for PCI Section 6.5 compliance and the items that are important for secure software development.

    3. The TOP 25 Errors List will be updated regularly and will be posted at both the SANS and MITRE sites
      CWE Top 25 Software Errors Site

      MITRE maintains the CWE (Common Weakness Enumeration) web site, with the support of the US Department of Homeland Security's National Cyber Security Division, presenting detailed descriptions of the top 25 Software errors along with authoritative guidance for mitigating and avoiding them. That site also contains data on more than 700 additional Software errors, design errors and architecture errors that can lead to exploitable vulnerabilities. CWE Web Site

    4. SAFECode - The Software Assurance Forum for Excellence in Code (members include EMC, Juniper, Microsoft, Nokia, SAP and Symantec) has produced two excellent publications outlining industry best practices for software assurance and providing practical advice for implementing proven methods for secure software development.

      Fundamental Practices for Secure Software Development 3rd Edition

      Overview of Software Integrity Controls

      Framework for Software Supply Chain Integrity

      Fundamental Practices for Secure Software Development

      Software Assurance: An Overview of Current Industry Best Practices

    5. Software Assurance Community Resources Site and DHS web sites

      As part of DHS risk mitigation efforts to enable greater resilience of cyber assets, the Software Assurance Program seeks to reduce software vulnerabilities, minimize exploitation, and address ways to routinely acquire, develop and deploy reliable and trustworthy software products with predictable execution, and to improve diagnostic capabilities to analyze systems for exploitable weaknesses.

    6. Nearly a dozen software companies offer automated tools that test programs for these errors.

    How Important Are the Top 25 Software Errors?

    We asked several of the participants why they thought this effort was important enough to merit a significant amount of their time and expertise. Here are a few of their answers. More are at the end of the announcement.
    Just wanted to commend the depth of the CWE/SANS Top 25. The code examples are particularly excellent. I have asked all my developers to read one of these each day for the next 25 days. I'm taking my own advice as well, and even though I'm still reading some of the "easy" ones (like SQL injection), I still find that I am learning new things about old topics.
    Mark E. Haase
    - OpenFISMA Project Manager, Endeavor Systems, Inc.
    The Top 25 provides much needed guidance for software developers focusing on eliminating software security defects in their products. If you're involved with software development at your organization and are looking to improve your product security posture, you need to read this.
    Robert Auger
    - Co Founder of The Web Application Security Consortium
    It's great to see the CWE/SANS Top 25 list continue to be maintained and mature. Relentlessly spreading the word about the most common security defects in programming is a vital need. The state of security in our software would without a doubt be much improved if everyone who touches software development reads and thoroughly understands this. Kudos.
    Kenneth R. van Wyk
    - KRvW Associates, LLC

      Contributors to the 2021 CWE Top 25:

        In alphabetical order: Adam Chaudry, Steve Christey Coley, Kerry Crouse, Kevin Davis, Devon Ellis, Parker Garrison, Christina Johns, Luke Malinowski, Rushi Purohit, Becky Powell, David Rothenberg, Alec Summers, and Brian Vohaska.

        Members of the NIST NVD Team that coordinated on the Top 25 include Christopher Turner, Robert Byers, and Vidya Ananthakrishna.