CVE-2026-42789
4.8 · MEDIUMOverview
CVE-2026-42789 is a medium-severity vulnerability affecting erlang erlang\/otp. It was published on May 27, 2026 and has a CVSS 3.1 base score of 4.8 (MEDIUM).
This vulnerability has a CVSS 3.1 base score of 4.8, rated MEDIUM. It can be exploited remotely over the network. No authentication or special privileges are required for exploitation.
Technical Description
Improper Following of a Certificate's Chain of Trust vulnerability in Erlang OTP public_key (pubkey_cert module) allows a non-CA certificate to be accepted as an intermediate issuer, enabling certificate chain forgery.
In lib/public_key/src/pubkey_cert.erl, pubkey_cert:validate_extensions/7 contains two flaws that together allow a certificate with basicConstraints cA:false and no keyUsage extension to be used as an intermediate issuer in a chain passed to public_key:pkix_path_validation/3: the cA:false clause recurses into the remaining extensions without rejecting the certificate when it is in issuer position, and the keyUsage check only fires when the extension is present, so a certificate lacking keyUsage entirely bypasses the keyCertSign enforcement.
Any party holding an end-entity certificate with basicConstraints cA:false and no keyUsage extension, issued by any CA in the victim's trust store, can use that certificate's private key to sign forged leaf certificates for arbitrary
Remediation
Check the references section for vendor advisories and patches from erlang. Update erlang\/otp to the latest patched version. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.
Affected Products
| Vendor | Product | Versions | Status |
|---|---|---|---|
| erlang | erlang\/otp | >= 17.0, < 26.2.5.21 | Affected |
References
Frequently Asked Questions
What is CVE-2026-42789?
CVE-2026-42789 is a medium-severity vulnerability affecting erlang erlang\/otp. It was published on May 27, 2026 and has a CVSS 3.1 base score of 4.8 (MEDIUM).
How severe is CVE-2026-42789?
This vulnerability has a CVSS 3.1 base score of 4.8, rated MEDIUM. It can be exploited remotely over the network. No authentication or special privileges are required for exploitation.
How do I fix or remediate CVE-2026-42789?
Check the references section for vendor advisories and patches from erlang. Update erlang\/otp to the latest patched version. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.
How can CyberStrike help with CVE-2026-42789?
CyberStrike's AI-powered security agents can automatically detect CVE-2026-42789 across your infrastructure using autonomous pentesting, DAST scanning, and HackBrowser. The platform continuously monitors for known vulnerabilities and provides actionable remediation guidance prioritized by real-world exploitability.
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