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GHSA-j7c9-79x7-8hpr
No affected components available
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. This audit was sponsored by ANSSI (French Cybersecurity Agency) based on their Open-Source security audit program.
Embargo List
If your organization runs Step CA in production and would like advance, embargoed notification of future security updates, visit https://u.step.sm/disclosure to request inclusion on our embargo list.
Stay safe, and thank you for helping us keep the ecosystem secure.
The vulnerability can be exploited over the network without needing physical access. It is difficult for an attacker to exploit this vulnerability and may require special conditions. An attacker needs high-level or administrative privileges. No user interaction is needed for the attacker to exploit this vulnerability. The impact is confined to the system where the vulnerability exists. There is a low impact on the integrity of the data. There is a high impact on the availability of the system.
Exploitation attempts have been detected. Elevated vigilance and prompt remediation are advised.
The exploit probability is very low. The vulnerability is unlikely to be exploited in the next 30 days.
We did not find any exploit available. Neither in GitHub repositories nor in the Exploit-Database.
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