CVE-2026-45309: AsyncSSH `AuthorizedKeysFile %u` path traversal allows attacker-selected authorized keys to authenticate a traversal username

High 8.2 EPSS 0.6% OpenSSH

AsyncSSH is a Python package which provides an asynchronous client and server implementation of the SSHv2 protocol on top of the Python asyncio framework. Prior to 2.23.0, AsyncSSH expands the OpenSSH-compatible AuthorizedKeysFile %u token in asyncssh/config.py, asyncssh/connection.py, asyncssh/auth_keys.py, and asyncssh/misc.py with the raw SSH username during pre-authentication server config reload, allowing a server configured with AuthorizedKeysFile authorized_keys/%u to read an authorized-keys file outside the intended directory when the SSH username contains /, \, or .. path traversal segments and authenticate with an attacker-selected key file. This issue is fixed in version 2.23.0.

CVE-2026-45309CVE identifier
8.2CVSS 4.0 base score (high)
0.6%EPSS: chance of exploitation in the next 30 days (higher than 48% of CVEs)
2026-07-17published

What do these terms mean? CVE · CVSS score · exploited (KEV) · EPSS · backported fix · all terms

What to do now

Check whether you run OpenSSH and which version (commands below).
Install the fixed version for your system: see “Patch it” below.
sudo systemctl restart ssh (Debian/Ubuntu) or sshd (RHEL/SUSE/Fedora/Arch/Amazon); Alpine: rc-service sshd restart; FreeBSD: service sshd restart

Affected and fixed versions

Affected:

ronf asyncssh < 2.23.0

Patch it

Use the commands for your system. Distribution packages often keep an older version number with the fix backported, so compare with the fixed package versions in the table below, not only with the upstream version.

Debian

sudo apt update
sudo apt install --only-upgrade openssh-server openssh-client

Ubuntu

sudo apt update
sudo apt install --only-upgrade openssh-server openssh-client

RHEL, AlmaLinux, Rocky, Oracle

sudo dnf upgrade --refresh openssh-server openssh

Fedora

sudo dnf upgrade --refresh openssh-server openssh

SUSE / openSUSE

sudo zypper refresh
sudo zypper update openssh openssh-server

Amazon Linux

sudo dnf upgrade --releasever=latest openssh-server openssh

Arch Linux

sudo pacman -Syu

Alpine

apk update && apk upgrade openssh openssh-server

FreeBSD

pkg update && pkg upgrade openssh-portable (port; the base-system sshd is patched with freebsd-update)

General update steps for every system are on the Linux and Unix & BSD pages; after updating, see which services to restart.

Fix status in Linux distributions

Release	Package	Status	Fixed version / advisory
Debian 12	`python-asyncssh`	not fixed yet
Debian 13	`python-asyncssh`	not fixed yet
Debian testing	`python-asyncssh`	fixed	`2.23.0-1`

From the Debian security tracker, Ubuntu CVE tracker and Red Hat Security Data API, refreshed every few hours.

Sources

Page generated automatically from official sources on 2026-11-03 18:05 UTC. Always confirm with your vendor's advisory.