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DEBIAN-CVE-2026-62949

Type: advisorySource: OSV1 source record

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.

Announced 16 Sept 2026Group revision 1

Original source ↗

DEBIAN-CVE-2026-62949

Primary source · Revision 1

Imported from structured advisory data. Source references identify upstream records or fields; verify affected versions and your deployed configuration.

Security context

Source reference: osv:DEBIAN-CVE-2026-62949

python-asyncssh

Source reference: /affected/0/package/name

Affected versions: 2.10.1-2
Source reference: /affected/0/versions
2.10.1-2+deb12u1
Source reference: /affected/0/versions
2.10.1-2+deb12u2
Source reference: /affected/0/versions
2.15.0-1
Source reference: /affected/0/versions
2.16.0-1
Source reference: /affected/0/versions
2.17.0-1
Source reference: /affected/0/versions
2.17.0-2
Source reference: /affected/0/versions
2.18.0-1
Source reference: /affected/0/versions
2.19.0-1
Source reference: /affected/0/versions
2.20.0-1
Source reference: /affected/0/versions
2.21.0-1
Source reference: /affected/0/versions
2.21.1-1
Source reference: /affected/0/versions
2.22.0-1
Source reference: /affected/0/versions
2.22.0-2
Source reference: /affected/0/versions
2.23.0-1
Source reference: /affected/0/versions
2.24.0-1
Source reference: /affected/0/versions
2.24.0-2
Source reference: /affected/0/versions
Fixed versions: Not stated in this record
Prerequisites: Not stated in this record

python-asyncssh

Source reference: /affected/1/package/name

Affected versions: 2.20.0-1
Source reference: /affected/1/versions
2.21.0-1
Source reference: /affected/1/versions
2.21.1-1
Source reference: /affected/1/versions
2.22.0-1
Source reference: /affected/1/versions
2.22.0-2
Source reference: /affected/1/versions
2.23.0-1
Source reference: /affected/1/versions
2.24.0-1
Source reference: /affected/1/versions
2.24.0-2
Source reference: /affected/1/versions
Fixed versions: Not stated in this record
Prerequisites: Not stated in this record

python-asyncssh

Source reference: /affected/2/package/name

Affected versions: 2.20.0-1
Source reference: /affected/2/versions
2.21.0-1
Source reference: /affected/2/versions
2.21.1-1
Source reference: /affected/2/versions
2.22.0-1
Source reference: /affected/2/versions
2.22.0-2
Source reference: /affected/2/versions
2.23.0-1
Source reference: /affected/2/versions
2.24.0-1
Source reference: /affected/2/versions
2.24.0-2
Source reference: /affected/2/versions
Fixed versions: Not stated in this record
Prerequisites: Not stated in this record

Structured affected-version data

Original package identities and version rules from this source.

[
  {
    "ranges": [
      {
        "type": "ECOSYSTEM",
        "events": [
          {
            "introduced": "0"
          }
        ]
      }
    ],
    "package": {
      "name": "python-asyncssh",
      "purl": "pkg:deb/debian/python-asyncssh?arch=source&distro=bookworm",
      "ecosystem": "Debian:12"
    },
    "versions": [
      "2.10.1-2",
      "2.10.1-2+deb12u1",
      "2.10.1-2+deb12u2",
      "2.15.0-1",
      "2.16.0-1",
      "2.17.0-1",
      "2.17.0-2",
      "2.18.0-1",
      "2.19.0-1",
      "2.20.0-1",
      "2.21.0-1",
      "2.21.1-1",
      "2.22.0-1",
      "2.22.0-2",
      "2.23.0-1",
      "2.24.0-1",
      "2.24.0-2"
    ],
    "database_specific": {
      "source": "https://storage.googleapis.com/debian-osv/debian-cve-osv/DEBIAN-CVE-2026-62949.json"
    },
    "ecosystem_specific": {
      "urgency": "not yet assigned"
    }
  },
  {
    "ranges": [
      {
        "type": "ECOSYSTEM",
        "events": [
          {
            "introduced": "0"
          }
        ]
      }
    ],
    "package": {
      "name": "python-asyncssh",
      "purl": "pkg:deb/debian/python-asyncssh?arch=source&distro=trixie",
      "ecosystem": "Debian:13"
    },
    "versions": [
      "2.20.0-1",
      "2.21.0-1",
      "2.21.1-1",
      "2.22.0-1",
      "2.22.0-2",
      "2.23.0-1",
      "2.24.0-1",
      "2.24.0-2"
    ],
    "database_specific": {
      "source": "https://storage.googleapis.com/debian-osv/debian-cve-osv/DEBIAN-CVE-2026-62949.json"
    },
    "ecosystem_specific": {
      "urgency": "not yet assigned"
    }
  },
  {
    "ranges": [
      {
        "type": "ECOSYSTEM",
        "events": [
          {
            "introduced": "0"
          }
        ]
      }
    ],
    "package": {
      "name": "python-asyncssh",
      "purl": "pkg:deb/debian/python-asyncssh?arch=source&distro=forky",
      "ecosystem": "Debian:14"
    },
    "versions": [
      "2.20.0-1",
      "2.21.0-1",
      "2.21.1-1",
      "2.22.0-1",
      "2.22.0-2",
      "2.23.0-1",
      "2.24.0-1",
      "2.24.0-2"
    ],
    "database_specific": {
      "source": "https://storage.googleapis.com/debian-osv/debian-cve-osv/DEBIAN-CVE-2026-62949.json"
    },
    "ecosystem_specific": {
      "urgency": "not yet assigned"
    }
  }
]

Publisher severity

No explicit severity was provided.

Event: #59426 · Revision 1
Added to Heist Feed: Sun, 25 Oct 2026 18:28:52 GMT
Publisher date: Wed, 16 Sep 2026 20:17:26 GMT

Read the original announcement

Revision history

25 Oct 2026DEBIAN-CVE-2026-62949 · Revision 1Source updated