CVE-2026-6679

Analyzed Analyzed - Analysis Complete

Heap Buffer Overflow in wolfSSL DTLS 1.3

Publication date: 2026-06-25

Last updated on: 2026-06-27

Assigner: wolfSSL Inc.

Description

A heap buffer overflow could occur in the DTLS 1.3 ACK serialization path before the connecting peer is authenticated. The buffer overflow was due to an integer truncation when computing the length of the ACK record-number list, causing an undersized buffer to be allocated and then overrun. This affects builds using DTLS 1.3 and wolfSSL version 5.9.0 and earlier. A fix was added to the 5.9.1 release.

CVSS Scores

EPSS Scores

Probability:
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Meta Information

Published

2026-06-25

Last Modified

2026-06-27

Generated

2026-07-16

AI Q&A

2026-06-26

EPSS Evaluated

2026-07-14

NVD

CVE-2026-6679

Affected Vendors & Products

Vendor	Product	Version / Range
wolfssl	wolfssl	From 5.4.0 (inc) to 5.9.1 (exc)

Helpful Resources

Exploitability

CWE

KEV

CWE ID	Description
CWE-190	The product performs a calculation that can produce an integer overflow or wraparound when the logic assumes that the resulting value will always be larger than the original value. This occurs when an integer value is incremented to a value that is too large to store in the associated representation. When this occurs, the value may become a very small or negative number.
CWE-197	Truncation errors occur when a primitive is cast to a primitive of a smaller size and data is lost in the conversion.
CWE-787	The product writes data past the end, or before the beginning, of the intended buffer.

Attack-Flow Graph

Compliance Impact

The provided information does not specify how the heap buffer overflow vulnerability in wolfSSL's DTLS 1.3 ACK serialization path impacts compliance with common standards and regulations such as GDPR or HIPAA.

Executive Summary

This vulnerability is a heap buffer overflow that occurs in the DTLS 1.3 ACK serialization path before the connecting peer is authenticated.

The overflow happens because of an integer truncation when calculating the length of the ACK record-number list, which leads to allocating a buffer that is too small and then overrunning it.

It affects wolfSSL versions 5.9.0 and earlier that use DTLS 1.3, and was fixed in version 5.9.1.

Impact Analysis

A heap buffer overflow can lead to serious security issues such as application crashes, data corruption, or potentially arbitrary code execution.

Since this occurs before the connecting peer is authenticated, an attacker could exploit this vulnerability remotely without needing prior access.

The CVSS base score of 8.8 indicates a high severity, meaning the impact on confidentiality, integrity, and availability could be significant.

Mitigation Strategies

To mitigate this vulnerability, you should upgrade wolfSSL to version 5.9.1 or later, as the fix for the heap buffer overflow was added in that release.

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