# CVE-2026-55962: TLS 1.3 post-handshake authentication: server accepts Finished without client Certificate/CertificateVerify


- **Severity:** Medium 6.0 (`CVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N`)
- **Exploited in the wild:** Not known
- **Fix available:** Yes
- **Published:** 25 Jun 2026
- **Updated:** 26 Jun 2026
- **Also known as:** DEBIAN-CVE-2026-55962, GHSA-gq94-hf88-g4wv, JLSEC-2026-737, UBUNTU-CVE-2026-55962

## What is CVE-2026-55962?

CVE-2026-55962 is a medium-severity vulnerability in Wolfssl Wolfssl, published on 25 Jun 2026. 

### Official description

TLS 1.3 post-handshake authentication (PHA) issue where a server could accept a client's Finished message without the client having sent a Certificate and CertificateVerify. The post-handshake-auth exemption that allows an empty/absent peer certificate was only intended for the initial handshake, but it was also being applied while a post-handshake CertificateRequest was still outstanding. The check is now scoped to the initial handshake only: on the server, once a post-handshake CertificateRequest has been sent (certReqCtx is set), a peer certificate and a valid CertificateVerify are required again before the Finished is accepted, with empty-certificate handling following the configured verify mode (FAIL_IF_NO_PEER_CERT) just as during first-handshake client authentication. Only affects TLS 1.3 servers built with post-handshake authentication support (WOLFSSL_POST_HANDSHAKE_AUTH / --enable-postauth, included in --enable-all) that enable WOLFSSL_VERIFY_POST_HANDSHAKE and request a client certificate after the handshake via wolfSSL_request_certificate(). Clients, and servers that do not use post-handshake authentication, are unaffected.

Weakness: CWE-287 (Improper Authentication)

## Which versions are affected by CVE-2026-55962?

It affects 1 product.


Products: Wolfssl Wolfssl.

## How do I fix CVE-2026-55962?

Upgrade to a fixed version.

## Is CVE-2026-55962 being exploited?

There is no known exploitation of CVE-2026-55962 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-2026-55962 and fix it if it is affected.

What it is: CVE-2026-55962 is a medium-severity vulnerability in Wolfssl Wolfssl, published on 25 Jun 2026. 
Exploitation: There is no known exploitation of CVE-2026-55962 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-2026-55962/ (Markdown: https://insights.sbomify.com/CVE-2026-55962/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-55962
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-55962
- OSV: https://osv.dev/vulnerability/CVE-2026-55962

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-55962/
Summaries are generated and may contain mistakes; the official description above is the record.