{
  "affected": [
    {
      "ranges": [
        {
          "database_specific": {
            "extracted_events": [
              {
                "introduced": "0"
              },
              {
                "fixed": "2.24.0"
              }
            ],
            "source": [
              "AFFECTED_FIELD",
              "REFERENCES"
            ]
          },
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "756cbae5350789ce9735f15f704bae9b5a3608b8"
            },
            {
              "fixed": "9c354270c009285525e126721e8ed5fbed1f8a67"
            },
            {
              "fixed": "3577224af6489a8c2653ce5b60dccfa5979f5ce0"
            }
          ],
          "repo": "https://github.com/ronf/asyncssh",
          "type": "GIT"
        }
      ]
    }
  ],
  "aliases": [
    "GHSA-rw4j-r22c-9gc3"
  ],
  "database_specific": {
    "cna_assigner": "GitHub_M",
    "cwe_ids": [
      "CWE-835"
    ],
    "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/62xxx/CVE-2026-62949.json"
  },
  "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.",
  "id": "CVE-2026-62949",
  "modified": "2026-09-19T03:30:43.051124626Z",
  "published": "2026-09-16T20:00:46.657Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/ronf/asyncssh/releases/tag/v2.24.0"
    },
    {
      "type": "ADVISORY",
      "url": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/62xxx/CVE-2026-62949.json"
    },
    {
      "type": "ADVISORY",
      "url": "https://github.com/ronf/asyncssh/security/advisories/GHSA-rw4j-r22c-9gc3"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-62949"
    },
    {
      "type": "FIX",
      "url": "https://github.com/ronf/asyncssh/commit/756cbae5350789ce9735f15f704bae9b5a3608b8"
    },
    {
      "type": "FIX",
      "url": "https://github.com/ronf/asyncssh/commit/9c354270c009285525e126721e8ed5fbed1f8a67"
    }
  ],
  "schema_version": "1.9.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H",
      "type": "CVSS_V3"
    }
  ],
  "summary": "AsyncSSH: asyncio event-loop freeze via SSH maximum packet size = 0 in SSH_MSG_CHANNEL_OPEN / OPEN_CONFIRMATION"
}