CVE-2026-48108 Russh: SSH identification parsing accepted non-canonical client banners and did not bound pre-banner input
Remote attackers can exhaust server resources during SSH connection setup by sending malformed identification strings, affecting applications using the russh library.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-48108?
CVE-2026-48108 is a medium-severity denial of service vulnerability in Eugeny russh, published on 10 Jun 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
Russh is a Rust SSH client & server library. From version 0.34.0-beta.1 to before version 0.61.0, russh did not enforce the SSH identification-string rules as deliberately as OpenSSH. In particular, the server-side identification reader used the same permissive path as the client, allowing pre-banner lines from clients, and the reader did not enforce a bounded number of pre-banner lines. For a library server built on russh, this could allow a remote peer to hold connection setup resources in the cleartext pre-authentication phase with malformed identification input that should have been rejected early. This issue has been patched in version 0.61.0.
Weakness: CWE-20
Which versions are affected by CVE-2026-48108?
2 open source packages ship an affected version, including russh.
| Package | Affected | Fixed in |
|---|---|---|
russh crates.io | From 0.34.0-beta.1 | 0.61.0 |
russh crates.io | From 0.34.0-beta.1 | 0.61.0 |
How do I fix CVE-2026-48108?
Upgrade russh to 0.61.0 or later.
Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.
Is CVE-2026-48108 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-48108 exists.
Sources
Also known as DEBIAN-CVE-2026-48108, GHSA-76r6-x97p-67vr.