# CVE-2026-93304: (D)TLS 1.2 client accepts early ChangeCipherSpec before ClientKeyExchange

> An attacker can inject early ChangeCipherSpec messages to bypass TLS handshake validation, allowing them to send data accepted as authentic by the client.

- **Severity:** Medium 6.3 (`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`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 27 Sep 2026
- **Updated:** 29 Sep 2026
- **Also known as:** AZL-105194, DEBIAN-CVE-2026-93304, GHSA-vpg5-xh2g-4x3c, UBUNTU-CVE-2026-93304

## What is CVE-2026-93304?

CVE-2026-93304 is a medium-severity vulnerability in Wolfssl Wolfssl, published on 27 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

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.

Weakness: CWE-696 (Incorrect Behavior Order)

## Which versions are affected by CVE-2026-93304?

It affects 1 product.


Products: Wolfssl Wolfssl.

## How do I fix CVE-2026-93304?

No fix has been published for CVE-2026-93304 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-93304 being exploited?

There is no known exploitation of CVE-2026-93304 in the wild and no public exploit code.

## Other vulnerabilities in Wolfssl Wolfssl

- [CVE-2024-5991](https://insights.sbomify.com/CVE-2024-5991/): Buffer overread in domain name matching (critical 10.0)
- [CVE-2021-37155](https://insights.sbomify.com/CVE-2021-37155/): Security feature bypass in n/a (critical 9.8)
- [CVE-2020-36177](https://insights.sbomify.com/CVE-2020-36177/): Memory corruption in n/a (critical 9.8)
- [CVE-2014-2896](https://insights.sbomify.com/CVE-2014-2896/): Memory corruption in n/a (critical 9.8)
- [CVE-2014-2897](https://insights.sbomify.com/CVE-2014-2897/): Memory corruption in n/a (critical 9.8)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-93304 and fix it if it is affected.

What it is: CVE-2026-93304 is a medium-severity vulnerability in Wolfssl Wolfssl, published on 27 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-93304 in the wild and no public exploit code.

Affected product: Wolfssl Wolfssl. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-93304/ (Markdown: https://insights.sbomify.com/CVE-2026-93304/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-93304
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-93304
- OSV: https://osv.dev/vulnerability/CVE-2026-93304

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-93304/
Summaries are generated and may contain mistakes; the official description above is the record.