CVE-2026-48108: Eugeny Russh resource exhaustion in SSH identification parsing

CVE-2026-48108 · Severity: medium · CVSS 5.3 · Published 2026-06-10

Russh is a library used to implement SSH servers and clients in the Rust programming language. A vulnerability in how the library handles initial connection messages allows a remote attacker to send an unlimited number of invalid lines before identifying themselves. This can be used to consume server resources and keep connections open indefinitely, potentially leading to a denial of service for legitimate users.

Technologies: russh (crates.io), Eugeny Tabby. Vendors: crates.io, Eugeny.

Quick answers

Is CVE-2026-48108 exploited in the wild?
No. Junglewise Threat Intelligence has no report of CVE-2026-48108 being exploited in the wild.
How severe is CVE-2026-48108?
Medium severity, with a CVSS score of 5.3, published 10 June 2026.
Which products and versions are affected?
russh (crates.io) SEMVER:introduced=0.34.0-beta.1,fixed=0.61.0; Eugeny Tabby >= 0.34.0-beta.1, < 0.61.0.
Is there a fix for CVE-2026-48108?
Yes. russh (crates.io): upgrade to 0.61.0 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
How is CVE-2026-48108 attacked?
It is attacked over the network, in a software library.
Am I affected by CVE-2026-48108?
Check whether you run russh (crates.io) or Eugeny Tabby at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

How to fix

  • russh (crates.io): upgrade to 0.61.0 or later
    cargo update -p russh

Technical details

The russh library's identification reader (read_ssh_id) failed to enforce RFC 4253 requirements for server-side parsing. Specifically, it used the same permissive logic for both clients and servers, allowing clients to send pre-banner lines that should only be permitted from servers. Furthermore, the parser did not implement a limit on the number of pre-banner lines or strict line length limits. An unauthenticated remote attacker can exploit this by sending a continuous stream of non-SSH lines, keeping the connection in a pre-authentication state and consuming server resources. The vulnerability also functions as a parser-state oracle, allowing for cheaper fingerprinting of the server's parser behavior. The issue is fixed in version 0.61.0 by introducing stricter client-identification reading and explicit line count/length limits.

Affected products

  • Eugeny russh >= 0.34.0-beta.1, < 0.61.0

Identifiers

  • CVE-2026-48108
  • GHSA-76r6-x97p-67vr

Timeline

  • 2026-05-20: disclosed
  • 2026-06-10: advisory: NVD publication date
  • 2026-06-11: patched: Version 0.61.0 released

References

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