CVE-2026-73489 Eugeny CVE debrief

Who should care

Defenders managing SSH servers or clients based on the Russh library should assess their exposure to this vulnerability. This includes reviewing the version of Russh in use and ensuring it is upgraded to 0.62.4 or later if necessary. Additionally, system administrators and security professionals responsible for SSH services should be aware of the potential for denial-of-service attacks and monitor SSH logs for suspicious activity.

Why it matters

CVE-2026-73489 is a denial-of-service vulnerability in the Russh Rust SSH client and server library. An authenticated SSH client can cause a panic in the server by sending a pty-req channel request with over 130 terminal-mode records. Defenders should prioritize verifying exposure to this vulnerability in Russh-based SSH servers and clients, especially in environments where authenticated SSH access is common. The vulnerability is fixed in version 0.62.4.

• Denial of service through SSH service termination
• Potential for service disruption in environments relying on Russh-based SSH servers

Technical summary

The Russh library, a Rust implementation of an SSH client and server, is vulnerable to a denial-of-service attack. An authenticated SSH client can cause the server to panic by sending a pty-req channel request with more than 130 terminal-mode records. This panic occurs because the library stores terminal modes in a fixed 130-entry array but does not properly handle an increasing mode count, leading to an out-of-bounds slice construction and panic before the pty_request handler runs. The panic terminates the server session task without causing memory corruption. The issue is addressed in version 0.62.4 of the Russh library.

Defensive priority

Defenders should prioritize verifying exposure to this vulnerability in Russh-based SSH servers and clients, especially in environments where authenticated SSH access is common.

Recommended defensive actions

• Verify Russh version and upgrade to 0.62.4 if necessary
• Review SSH server and client configurations for exposure
• Monitor SSH logs for suspicious activity
• Check relevant monitoring, detection, and logs for exposed assets that need extra review.
• Track exceptions, retest remediated assets, and close the item only after evidence is documented.
• Review compensating controls for exposed systems while remediation is scheduled and verified.
• Plan vendor-supported updates or mitigations through normal change control where exposure is confirmed.

Evidence notes

The CVE record and NVD entry provide details on the vulnerability, including its description, CVSS score, and affected versions. The GitHub repository for Russh provides additional information on the fix in version 0.62.4.

Sources and references

Methodology and review provenance

AI-assisted synthesis based on stored public vulnerability evidence. System validation, approval state, and publication status do not by themselves establish human review of this revision. PatchSiren helps prioritize defensive review and does not prove exposure or remediation on any system.