Withdrawn by the publisher.

Affected: CleanStart: step

Multiple security vulnerabilities affect the step package. gRPC-Go is the Go language implementation of gRPC. See references for individual vulnerability details.

Step CA is an online certificate authority for secure, automated certificate management for DevOps. Prior to 0.29.0, there is an improper authorization check for SSH certificate revocation. This affects deployments configured with the SSHPOP provisioner. This vulnerability is fixed in 0.29.0.

Affected: Go: github.com/smallstep/certificates

## Summary An authorized attacker can bypass authorization checks and revoke any SSH certificate issued by Step CA by using a valid revocation token.

## Details Step CA users can obtain SSH certificates from a few provisioners. The SSHPOP provisioner allows revocation of the SSH certificate (preventing future certificate renewals) using a token. Due to a missing validity check, this token could be used to revoke any SSH certificate issued by the CA.

To create a token, an attacker must have access to the CA endpoint and a valid SSH certificate, meaning they were already authorized to obtain an SSH certificate. The attacker must also know the serial number of the certificate they want to revoke.

## Impact There is no way to mitigate this attack. It is recommended to update to v0.29.0 or newer.

## Fix In v0.29.0, the token validation logic was strengthened to bind each token to a specific SSH certificate serial number.

## Acknowledgements This issue was identified and reported by Gabriel Departout and Andy Russon, from [AMOSSYS](http://amossys.fr/). This audit was sponsored by [ANSSI](https://cyber.gouv.fr/) (French Cybersecurity Agency) based on [their Open-Source security audit program](https://cyber.gouv.fr/open-source-lanssi#:~:text=Financement%20d%27%C3%A9valuations%20de%20s%C3%A9curit%C3%A9%20de%20logiciels%20libres).

## Embargo List

If your organization runs Step CA in production and would like advance, embargoed notification of future security updates, visit http…