Case Study: Buffer Overflow in TLS Handshake Parser (CVE-2025-40123)

[Yagnapriyakatragunta]

This pull request submits a new secure coding case study for CVE-2025-40123, a critical buffer overflow in a TLS handshake extension parser used across IoT firmware platforms.

The case study explains how unsafe memory operations in C caused this overflow, how attackers could exploit it, how the vulnerability was fixed through stricter bounds checking, and systemic secure coding lessons for embedded developers.

Related GitHub Proposal Issue: #16

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[abuttner]

Please try to add more detail to this case study. Ideally you should use complete sentences and paragraphs to walk the reader through the vulnerable code, point out the specific line(s) where the mistake/weakness is, and then show how the developer fixed the issue by presenting the fixed code. Please see the existing case studies for examples of how this has been accomplished.

[stevechristeycoley]

Automated Analysis Results of This Use Case

Thank you for providing your use case! Apologies for the form letter, but it's a pleasure to see y'all :)

With technical knowledge work such as this project, it is important to structure information as well as possible, so that it can be processed automatically.

We also want to validate our inputs ;-)

So, this report contains the results of an automated analysis of the provided use case, looking for consistency with the documented format as covered in Section 3 "Case Study Structure" of the Style Guide.

Disclaimers:

• David Wheeler may provide guidance on how to handle these reports. We're grateful that you've put in this work already, and we don't want to burden you unnecessarily 'cuz you're probably busy :)
• Our style guide was not always 100% clear (as often happens early in technical knowledge work), so this analysis attempts to automatically resolve potential inconsistencies.
• This report is provided as a convenience. There may be some errors or omissions in this report.
• We will conduct deeper analysis at a later time.

Items are prioritized from Informative, Low, Medium, to High in terms of current importance to the project.

Analyzing Presence of Markdown

• [High] does not appear to have any markdown in it (no #, at least)

Parser Issues

The following issues were encountered by the parser used to analyze this file. This might explain potential errors and false positives in the subsequent analysis.

• [Info] Guessing that line 2 contains a new section 'Introduction'
• [Info] Guessing that line 71 contains a new section 'Exploit'
• [Info] Guessing that line 91 contains a new section 'Fix'
• [Info] Guessing that line 118 contains a new section 'Prevention'
• [Info] Guessing that line 154 contains a new section 'Conclusion'
• [Info] Guessing that line 158 contains a new section 'References'
• [Info] Guessing that line 168 contains a new section 'Contributions'

Section Analysis

• [High] Expected section name missing: 'Title'
  • Important: detailed analysis not performed for this missing section
• [High] Expected section name missing: 'Weakness'
  • Important: detailed analysis not performed for this missing section
• [High] Expected section name missing: 'Vulnerability'
  • Important: detailed analysis not performed for this missing section
• [High] Expected section name missing: 'Software'
  • Important: detailed analysis not performed for this missing section
• [High] 4 major section-name issues detected.
• [Med] Section 'Introduction' is expected to have 3 hash marks, but it has 0
• [Med] Section 'Exploit' is expected to have 3 hash marks, but it has 0
• [Med] Section 'Fix' is expected to have 3 hash marks, but it has 0
• [Med] Section 'Prevention' is expected to have 3 hash marks, but it has 0
• [Med] Section 'Conclusion' is expected to have 3 hash marks, but it has 0
• [Med] Section 'References' is expected to have 3 hash marks, but it has 0
• [Med] Section 'Contributions' is expected to have 3 hash marks, but it has 0

Analyzing Introduction Section

No issues found.

Analyzing Fix Section

• [Med] Fix section does not appear to contain a 'fixed file:' label
• [Med] No apparent source code ``` tags in Fix section

Analyzing References Section

No issues found.