CVE-2023-6936 Heap-buffer over-read with WOLFSSL_CALLBACKS

Medium 5.3 Published 20 Feb 2024 Updated 26 Mar 2025

A heap buffer over-read in wolfSSL allows attackers to read memory or cause crashes when debugging callbacks are enabled.

Exploited in the wild: Not known
Login needed: Not needed
Attackable: Over the internet
Victim action needed: Not needed
Fix: Available

What is CVE-2023-6936?

CVE-2023-6936 is a medium-severity memory corruption vulnerability in Wolfssl Wolfssl, published on 20 Feb 2024. An attacker can exploit it over the internet without logging in, with no action from the victim.

Official description

In wolfSSL prior to 5.6.6, if callback functions are enabled (via the WOLFSSL_CALLBACKS flag), then a malicious TLS client or network attacker can trigger a buffer over-read on the heap of 5 bytes (WOLFSSL_CALLBACKS is only intended for debugging).

Weakness: CWE-125, CWE-126

Which versions are affected by CVE-2023-6936?

It affects 1 product.

Products include Wolfssl Wolfssl.

How do I fix CVE-2023-6936?

Upgrade to a fixed version.

Upgrade to the fixed version. Memory-safe languages, compiler hardening and fuzzing prevent most new cases. More about Memory corruption.

Is CVE-2023-6936 being exploited?

There is no known exploitation of CVE-2023-6936 in the wild and no public exploit code.

All Wolfssl Wolfssl vulnerabilities

Sources

Also known as DEBIAN-CVE-2023-6936, GHSA-cwpg-8775-j56v, JLSEC-2026-678, UBUNTU-CVE-2023-6936.