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 2.24.0, _process_channel_open and _process_channel_open_confirmation in asyncssh/connection.py accept a peer-supplied send_pktsize value of zero. When channel data reaches SSHChannel._flush_send_buf in asyncssh/channel.py, the zero value causes each loop iteration to slice and remove zero bytes without reducing the send window, leaving the synchronous loop permanently true with no await point. A malicious SSH server can trigger the client path through SSH_MSG_CHANNEL_OPEN_CONFIRMATION before the first channel write, while an authenticated client can trigger the server path through SSH_MSG_CHANNEL_OPEN and freeze every current and future connection handled by the process. This vulnerability is fixed in 2.24.0.

There are packages installed that are affected by a vulnerability referenced in the following CVE:

  - 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 2.24.0, _process_channel_open and
    _process_channel_open_confirmation in asyncssh/connection.py accept a peer-supplied send_pktsize value of
    zero. When channel data reaches SSHChannel._flush_send_buf in asyncssh/channel.py, the zero value causes
    each loop iteration to slice and remove zero bytes without reducing the send window, leaving the
    synchronous loop permanently true with no await point. A malicious SSH server can trigger the client path
    through SSH_MSG_CHANNEL_OPEN_CONFIRMATION before the first channel write, while an authenticated client
    can trigger the server path through SSH_MSG_CHANNEL_OPEN and freeze every current and future connection
    handled by the process. This vulnerability is fixed in 2.24.0. (CVE-2026-62949)

The remote openSUSE 16 host has a package installed that is affected by a vulnerability as referenced in the openSUSE- SU-2026:21953-1 advisory.

    Changes in python-asyncssh:

    - CVE-2026-62949: denial of service via infinite loop when processing       zero-sized SSH packets (bsc#1280972)

Tenable has extracted the preceding description block directly from the SUSE security advisory.

Note that Nessus has not tested for this issue but has instead relied only on the application's self-reported version number.

The Linux/Unix host has one or more packages installed that are impacted by a vulnerability without a vendor supplied patch available.

  - 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 2.24.0, _process_channel_open and
    _process_channel_open_confirmation in asyncssh/connection.py accept a peer-supplied send_pktsize value of     zero. When channel data reaches SSHChannel._flush_send_buf in asyncssh/channel.py, the zero value causes     each loop iteration to slice and remove zero bytes without reducing the send window, leaving the     synchronous loop permanently true with no await point. A malicious SSH server can trigger the client path     through SSH_MSG_CHANNEL_OPEN_CONFIRMATION before the first channel write, while an authenticated client     can trigger the server path through SSH_MSG_CHANNEL_OPEN and freeze every current and future connection     handled by the process. This vulnerability is fixed in 2.24.0. (CVE-2026-62949)

Note that Nessus relies on the presence of the package as reported by the vendor.

ID	Name	Product	Family	Type	Severity
474827	Echo: python-asyncssh: security update to 2.20.0-1+e3	Tenable Cloud Security	Echo Local Security Checks	Local	medium
474827	Echo: python-asyncssh: security update to 2.20.0-1+e3	Tenable Self-Hosted Container Security	Echo Local Security Checks	Local	medium
350764	openSUSE 16 Security Update : python-asyncssh (openSUSE-SU-2026:21953-1)	Nessus	SuSE Local Security Checks	Local	medium
348199	Linux Distros Unpatched Vulnerability : CVE-2026-62949	Nessus	Misc.	Local	medium

Detections

Analytics

CVE-2026-62949

medium

Tenable Plugins

medium

medium

medium

medium