Eugeny Russh up to 0.63.1 Server Session session.rs resource consumption

Summaryinfo

A vulnerability categorized as critical has been discovered in Eugeny Russh up to 0.63.1. This vulnerability affects unknown code of the file russh/src/server/session.rs of the component Server Session Handler. The manipulation results in resource consumption. This vulnerability was named CVE-2026-102821. The attack may be performed from remote. There is no available exploit. It is advisable to upgrade the affected component.

Detailsinfo

A vulnerability classified as critical has been found in Eugeny Russh up to 0.63.1. Affected is an unknown functionality of the file russh/src/server/session.rs of the component Server Session Handler. The manipulation with an unknown input leads to a resource consumption vulnerability. CWE is classifying the issue as CWE-400. The product does not properly control the allocation and maintenance of a limited resource, thereby enabling an actor to influence the amount of resources consumed, eventually leading to the exhaustion of available resources. This is going to have an impact on availability. CVE summarizes:

Russh is a Rust SSH client and server library. Prior to 0.63.2, an authenticated remote peer can send SSH_MSG_KEXINIT without the required SSH_MSG_KEX_ECDH_INIT and then flood SSH_MSG_CHANNEL_OPEN messages while SessionKexState::InProgress prevents priority_receiver in russh/src/server/session.rs from being drained. The server continues processing network input and enqueues a ChannelOpenReply for each request on an unbounded channel, allowing one connection to grow memory until the process is terminated. This issue is fixed in version 0.63.2.

The advisory is available at github.com. This vulnerability is traded as CVE-2026-102821 since 09/29/2026. The exploitability is told to be easy. It is possible to launch the attack remotely. Technical details are known, but there is no available exploit. This vulnerability is assigned to T1499 by the MITRE ATT&CK project.

Upgrading to version 0.63.2 eliminates this vulnerability.

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Productinfo

Vendor

• Eugeny

Name

• Russh

Version

• 0.63.0
• 0.63.1

Website

• Product: https://github.com/Eugeny/russh/

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