Sceawere

Vulnerability Detail

CVE-2026-62949 Verified Sceawere Triage Sources: NVD / CISA KEV

Vulnerability Metadata

Severity
Medium
Score / CVSS
6.5
Creation Date
1d ago
Vendor
ronf
Product
asyncssh
Attack Type
CWE-835: Loop with Unreachable Exit Condition ('Infinite Loop')
Vector String
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
Attack Complexity
LOW

Narrative and Response

Description

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.

Executive Summary

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Technical Details

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Mitigations

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References

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Additional Metadata

{
  "score": "6.5",
  "pubDate": "2026-09-16T20:17:26.220Z",
  "pubdate": "2026-09-16T20:17:26.220Z"
}