UBUNTU-CVE-2026-62949

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Source
https://ubuntu.com/security/CVE-2026-62949
Import Source
https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-62949.json
JSON Data
https://api.osv.dev/v1/vulns/UBUNTU-CVE-2026-62949
Upstream
Published
2026-09-18T00:00:00Z
Modified
2026-09-18T12:30:36Z
Severity
  • 6.5 (Medium) CVSS_V3 - CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H CVSS Calculator
  • Ubuntu - medium
Summary
[none]
Details

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.

References

Affected packages

Ubuntu:16.04:LTS
python-asyncssh

Package

Name
python-asyncssh
Purl
pkg:deb/ubuntu/python-asyncssh?arch=source&distro=xenial

Affected ranges

Type
ECOSYSTEM
Events
Introduced
0 Unknown introduced version / All previous versions are affected

Affected versions

1.*
1.2.0-1
1.2.1-1
1.3.0-1

Ecosystem specific 

{
    "binaries": [
        {
            "binary_name": "python3-asyncssh",
            "binary_version": "1.3.0-1"
        }
    ]
}

Database specific

source 
"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-62949.json"
Ubuntu:20.04:LTS
python-asyncssh

Package

Name
python-asyncssh
Purl
pkg:deb/ubuntu/python-asyncssh?arch=source&distro=focal

Affected ranges

Type
ECOSYSTEM
Events
Introduced
0 Unknown introduced version / All previous versions are affected

Affected versions

1.*
1.12.2-1
1.12.2-1ubuntu0.1
1.12.2-1ubuntu0.2

Ecosystem specific 

{
    "binaries": [
        {
            "binary_name": "python3-asyncssh",
            "binary_version": "1.12.2-1ubuntu0.2"
        }
    ]
}

Database specific

source 
"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-62949.json"
Ubuntu:26.04:LTS
python-asyncssh

Package

Name
python-asyncssh
Purl
pkg:deb/ubuntu/python-asyncssh?arch=source&distro=resolute

Affected ranges

Type
ECOSYSTEM
Events
Introduced
0 Unknown introduced version / All previous versions are affected

Affected versions

2.*
2.20.0-1
2.21.1-1

Ecosystem specific 

{
    "binaries": [
        {
            "binary_name": "python3-asyncssh",
            "binary_version": "2.21.1-1"
        }
    ]
}

Database specific

source 
"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-62949.json"
Ubuntu:Pro:18.04:LTS
python-asyncssh

Package

Name
python-asyncssh
Purl
pkg:deb/ubuntu/python-asyncssh?arch=source&distro=esm-apps%2Fbionic

Affected ranges

Type
ECOSYSTEM
Events
Introduced
0 Unknown introduced version / All previous versions are affected

Affected versions

1.*
1.8.1-2
1.11.0-2
1.11.1-1
1.11.1-1ubuntu0.1~esm1
1.11.1-1ubuntu0.1~esm2

Ecosystem specific 

{
    "binaries": [
        {
            "binary_name": "python3-asyncssh",
            "binary_version": "1.11.1-1ubuntu0.1~esm2"
        }
    ]
}

Database specific

source 
"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-62949.json"
Ubuntu:Pro:22.04:LTS
python-asyncssh

Package

Name
python-asyncssh
Purl
pkg:deb/ubuntu/python-asyncssh?arch=source&distro=esm-apps%2Fjammy

Affected ranges

Type
ECOSYSTEM
Events
Introduced
0 Unknown introduced version / All previous versions are affected

Affected versions

2.*
2.5.0-1
2.5.0-1ubuntu0.1~esm1
2.5.0-1ubuntu0.1
2.5.0-1ubuntu0.1+esm1

Ecosystem specific 

{
    "binaries": [
        {
            "binary_name": "python3-asyncssh",
            "binary_version": "2.5.0-1ubuntu0.1+esm1"
        }
    ]
}

Database specific

source 
"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-62949.json"
Ubuntu:Pro:24.04:LTS
python-asyncssh

Package

Name
python-asyncssh
Purl
pkg:deb/ubuntu/python-asyncssh?arch=source&distro=esm-apps%2Fnoble

Affected ranges

Type
ECOSYSTEM
Events
Introduced
0 Unknown introduced version / All previous versions are affected

Affected versions

2.*
2.10.1-2
2.10.1-2ubuntu0.1
2.10.1-2ubuntu0.1+esm1

Ecosystem specific 

{
    "binaries": [
        {
            "binary_name": "python3-asyncssh",
            "binary_version": "2.10.1-2ubuntu0.1+esm1"
        }
    ]
}

Database specific

source 
"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-62949.json"