---
id: CVE-2026-93304
title: >-
  A (D)TLS 1.2 client can accept a ChangeCipherSpec message before it has sent
  its ClientKeyExchange
summary: >-
  A (D)TLS 1.2 client can accept a ChangeCipherSpec message before it has sent
  its ClientKeyExchange. No master secret has been derived at that point, so the
  client installs read keys derived from a known (deterministic) key and checks
  the…
severity: medium
cvss: 6.3
cvssVector: 'CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N'
cwe:
  - CWE-696
vendor: wolfSSL
product: wolfSSL
affected:
  - wolfSSL >= 4.7.0 <= 5.9.2
published: '2026-09-27'
updated: '2026-09-27'
sourceUpdated: '2026-09-27T10:16:59.563'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-93304'
references:
  - url: 'https://github.com/wolfSSL/wolfssl/pull/11458'
    label: facts@wolfssl.com
tags:
  - nvd
  - cve.org
cvssSource: cna
ingestedAt: '2026-09-27T09:45:46.034Z'
---

## Overview

A (D)TLS 1.2 client can accept a ChangeCipherSpec message before it has sent its ClientKeyExchange. No master secret has been derived at that point, so the client installs read keys derived from a known (deterministic) key and checks the server's Finished against that same key. An out-of-order ChangeCipherSpec can therefore be used by an attacker to complete the handshake in place of the server and send data the client accepts as authentic. The client's own traffic still uses correctly derived keys, so the attacker cannot read it, and the genuine server never completes the handshake. DTLS 1.2 clients are exposed because a datagram read can deliver the out-of-order records on its own. TLS 1.2 clients are exposed when the application supplies received bytes with wolfSSL_inject() or enables read ahead. For certificate suites, the attacker must be in a man-in-the-middle position. For PSK (Pre Shared Key) connections, any fake server can succeed without knowing the PSK.

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.