CVE-2026-62949
- Source
- https://cve.org/CVERecord?id=CVE-2026-62949
- Import Source
- https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-62949.json
- JSON Data
- https://api.osv.dev/v1/vulns/CVE-2026-62949
- Aliases
- Downstream
- Published
- 2026-09-16T20:00:46Z
- Modified
- 2026-09-19T03:30:43Z
- 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
- Summary
- AsyncSSH: asyncio event-loop freeze via SSH maximum packet size = 0 in SSH_MSG_CHANNEL_OPEN / OPEN_CONFIRMATION
- 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.
- 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" }- References
-
- https://github.com/ronf/asyncssh/releases/tag/v2.24.0
- https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/62xxx/CVE-2026-62949.json
- https://github.com/ronf/asyncssh/security/advisories/GHSA-rw4j-r22c-9gc3
- https://nvd.nist.gov/vuln/detail/CVE-2026-62949
- https://github.com/ronf/asyncssh/commit/756cbae5350789ce9735f15f704bae9b5a3608b8
- https://github.com/ronf/asyncssh/commit/9c354270c009285525e126721e8ed5fbed1f8a67