---
id: CVE-2026-102821
title: Russh is a Rust SSH client and server library
summary: >-
  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::InProgre…
severity: medium
cvss: 6.5
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H'
cwe:
  - CWE-400
  - CWE-770
vendor: Eugeny
product: russh
affected:
  - russh < 0.63.2
published: '2026-09-29'
updated: '2026-09-30'
sourceUpdated: '2026-09-30T20:17:23.793'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-102821'
references:
  - url: >-
      https://github.com/Eugeny/russh/commit/a282af361ac99bc76b80876d1aae128e89dbf66b
    label: security-advisories@github.com
  - url: 'https://github.com/Eugeny/russh/releases/tag/v0.63.2'
    label: security-advisories@github.com
  - url: 'https://github.com/Eugeny/russh/security/advisories/GHSA-35g8-35p8-c8fw'
    label: security-advisories@github.com
  - url: 'https://github.com/Eugeny/russh/security/advisories/GHSA-35g8-35p8-c8fw'
    label: 134c704f-9b21-4f2e-91b3-4a467353bcc0
  - url: >-
      https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-102821.json
  - url: 'https://access.redhat.com/security/cve/CVE-2026-102821'
  - url: 'https://bugzilla.redhat.com/show_bug.cgi?id=2543501'
  - url: 'https://www.cve.org/CVERecord?id=CVE-2026-102821'
  - url: 'https://nvd.nist.gov/vuln/detail/CVE-2026-102821'
  - url: 'https://github.com/advisories/GHSA-35g8-35p8-c8fw'
  - url: 'https://github.com/Eugeny/russh'
  - url: 'https://access.redhat.com/errata/RHSA-2026:74586'
tags:
  - nvd
  - cve.org
  - exploit-available
  - csaf
  - vex
  - red-hat
  - ghsa
  - rust
  - osv
exploitAvailable: true
ssvc:
  exploitation: poc
  automatable: 'no'
  technicalImpact: partial
  timestamp: '2026-09-30T19:34:47.748081Z'
epss: 0.00358
epssPercentile: 0.29384
ingestedAt: '2026-09-29T18:42:35.835Z'
aliases:
  - GHSA-35g8-35p8-c8fw
ecosystem: rust
patched:
  - russh 0.63.2
---

## Overview

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.

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.

## Vendor advisories

- **Red Hat VEX** · Moderate · affected: Red Hat Hardened Images · no fix planned: Red Hat Hardened Images · updated 2026-09-29 · [vex](https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-102821.json)
- **RHSA-2026:74586** · Red Hat · fixed in: Red Hat Hardened Images · released 2026-10-01 · [advisory](https://access.redhat.com/errata/RHSA-2026:74586)

## Package advisory (CVE-2026-102821)

Affected packages:

- `russh <= 0.63.1`

Patched in:

- `russh 0.63.2`

Source: https://github.com/advisories/GHSA-35g8-35p8-c8fw