# CVE-2026-55964: Chain intermediate CA:TRUE without keyCertSign accepted as a signing CA (temporary CA exemption)

> Attackers can bypass certificate validation checks in wolfSSL's OpenSSL compatibility mode by using intermediate CAs lacking keyCertSign, potentially enabling man-in-the-middle attacks.

- **Severity:** Medium 6.3 (`CVSS:4.0/AV:N/AC:L/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:** Yes
- **Published:** 25 Jun 2026
- **Updated:** 26 Jun 2026
- **Also known as:** DEBIAN-CVE-2026-55964, GHSA-68g3-7fhp-7rg3, JLSEC-2026-738, UBUNTU-CVE-2026-55964

## What is CVE-2026-55964?

CVE-2026-55964 is a medium-severity vulnerability in Wolfssl Wolfssl, published on 25 Jun 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

Chain intermediate CA:TRUE without keyCertSign accepted as a signing CA. Intermediate CA certificates are required to have the keyCertSign key usage when a Key Usage extension is present, but chain-supplied temporary CAs (WOLFSSL_TEMP_CA) added while building a certificate path were previously exempted from this check, so an intermediate asserting CA:TRUE but lacking keyCertSign was accepted as a signing CA. The check now applies to chain-supplied temporary CAs as well; only operator-loaded root certificates (WOLFSSL_USER_CA) and self-signed roots remain exempt. Per RFC 5280 an absent Key Usage extension implies all usages, so the requirement is enforced only when the extension is actually present (extKeyUsageSet). Affects the OpenSSL-compatibility certificate-path-building path (X509_verify_cert / X509_STORE, OPENSSL_EXTRA/OPENSSL_ALL), where untrusted chain intermediates are added as temporary CAs; native (non-OpenSSL-compat) certificate verification does not create temporary CAs and is unaffected. Within those builds, the check applies unless ALLOW_INVALID_CERTSIGN is defined.

Weakness: CWE-295 (Improper Certificate Validation)

## Which versions are affected by CVE-2026-55964?

It affects 1 product.


Products: Wolfssl Wolfssl.

## How do I fix CVE-2026-55964?

Apply the vendor's patch.

## Is CVE-2026-55964 being exploited?

There is no known exploitation of CVE-2026-55964 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-2026-55964 and fix it if it is affected.

What it is: CVE-2026-55964 is a medium-severity vulnerability in Wolfssl Wolfssl, published on 25 Jun 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-2026-55964 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-2026-55964/ (Markdown: https://insights.sbomify.com/CVE-2026-55964/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-55964
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-55964
- OSV: https://osv.dev/vulnerability/CVE-2026-55964

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-55964/
Summaries are generated and may contain mistakes; the official description above is the record.