Executive Summary

CVE-2026-5448 is a buffer overflow vulnerability in the wolfSSL library related to handling X.509 certificate validity dates in the functions wolfSSL_X509_notBefore and wolfSSL_X509_notAfter.

The vulnerability occurs because these getter functions copy date data into fixed-size buffers without adequate bounds checking, which can lead to overflow when parsing crafted X.509 certificates.

This issue is triggered only when these two APIs are called directly from an application and does not affect TLS or certificate verification operations in wolfSSL.

The root cause involves a mismatch in allowed date length sizes between setter and getter functions, where setters allow up to 32 bytes but getters safely handle only up to 30 bytes, potentially causing failures or crashes.

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Impact Analysis

This vulnerability can lead to buffer overflow when an application directly calls the affected getter functions with crafted X.509 certificates.

Such buffer overflows may cause application crashes or undefined behavior, potentially leading to denial of service or other stability issues.

Additionally, the getter functions may return NULL unexpectedly if the date length is too large, and if the calling application does not handle this properly, it could result in crashes.

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Detection Guidance

This vulnerability occurs specifically when applications directly call the wolfSSL APIs wolfSSL_X509_notBefore and wolfSSL_X509_notAfter to parse date fields from crafted X.509 certificates. Detection involves identifying usage of these APIs in your application code and monitoring for abnormal behavior such as NULL returns or crashes related to these calls.

Since the vulnerability is triggered by crafted certificates with oversized date fields, you can attempt to detect it by testing your application with certificates containing manipulated notBefore and notAfter date fields exceeding safe lengths (greater than 30 bytes).

There are no specific network commands or signatures provided to detect exploitation on the network level because this vulnerability is not triggered during normal TLS or certificate verification operations in wolfSSL.

For system-level detection, you can:

• Review application logs for crashes or NULL pointer dereferences related to calls to wolfSSL_X509_notBefore or wolfSSL_X509_notAfter.
• Use debugging or instrumentation tools to trace calls to these APIs and check if they return NULL unexpectedly.
• Manually test your application with crafted certificates having date fields longer than 30 bytes to observe if the application handles them safely.

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Mitigation Strategies

Immediate mitigation steps include updating the wolfSSL library to version 5.9.1 or later, where bounds checks have been added to the getter and setter functions handling X.509 date fields to prevent buffer overflows.

If updating is not immediately possible, ensure that your application does not directly call wolfSSL_X509_notBefore or wolfSSL_X509_notAfter APIs with untrusted certificates or data.

Additionally, validate and sanitize any X.509 certificate date fields before passing them to these APIs, ensuring the date lengths do not exceed 30 bytes.

Monitor your application for unexpected NULL returns from these getter functions and handle such cases gracefully to avoid crashes.

Consider adding additional test coverage in your environment to cover boundary cases related to date field lengths in certificates.

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Compliance Impact

The provided information does not specify any direct impact of this vulnerability on compliance with common standards and regulations such as GDPR or HIPAA.

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