Bug 2501842 (CVE-2026-45309)

Summary:	CVE-2026-45309 asyncssh: AsyncSSH: Authentication bypass due to path traversal in username during pre-authentication
Product:	[Other] Security Response	Reporter:	OSIDB Bzimport <bzimport>
Component:	vulnerability	Assignee:	Product Security DevOps Team <prodsec-dev>
Status:	NEW ---	QA Contact:
Severity:	medium	Docs Contact:
Priority:	medium
Version:	unspecified	CC:	amctagga, aoconnor, bniver, flucifre, gmeno, groman, mbenjamin, mhackett, sostapov, vereddy
Target Milestone:	---	Keywords:	Security
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Hardware:	All
OS:	Linux
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Doc Text:	A flaw was found in AsyncSSH, a Python package for SSHv2 protocol implementation. A remote attacker can exploit a path traversal vulnerability by manipulating the SSH username during pre-authentication. This allows the attacker to read sensitive authorized-keys files from unintended directories, potentially leading to unauthorized authentication and system access.	Story Points:	---
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oVirt Team:	---	RHEL 7.3 requirements from Atomic Host:
Cloudforms Team:	---	Target Upstream Version:
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Description OSIDB Bzimport 2026-07-17 19:01:52 UTC

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.