CVE catalog
CVE-2026-62949
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 _p
- Severity
- Medium · CVSS 6.5
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H - Published
- Updated
- Source
- [NVD] · [CVE record]
- EPSS
- 0.39% · Oct 25, 2026
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.
Vulnerable and fixed packages
Distribution-reported package versions and fixes. These do not depend on matching against the OpenFactory package catalog.
| Distribution | Package | Release | Version | Status |
|---|---|---|---|---|
| Debian | python-asyncssh | sid | 2.24.0-2 | vulnerable |
| Debian | python-asyncssh | forky | 2.24.0-2 | vulnerable |
| Debian | python-asyncssh | trixie | 2.20.0-1 | vulnerable |
| Debian | python-asyncssh | bookworm | 2.10.1-2+deb12u2 | vulnerable |
| Debian | python-asyncssh | bookworm-security | 2.10.1-2+deb12u1 | vulnerable |
| Pip | asyncssh | Not reported | 2.24.0 | fixed |
| Opensuse | python-asyncssh | leap 16.0 | 2.21.0-bp160.2.1 | fixed |
Fixed-version evidence
| Distribution | Package | Type | Release | Fixed version | Urgency | Origin | Bugs |
|---|---|---|---|---|---|---|---|
| Debian | python-asyncssh | source | sid | (unfixed) | not yet assigned | Not reported | [1148448] |
| Debian | python-asyncssh | source | forky | (unfixed) | not yet assigned | Not reported | [1148448] |
| Debian | python-asyncssh | source | trixie | (unfixed) | not yet assigned | Not reported | [1148448] |
| Debian | python-asyncssh | source | bookworm | (unfixed) | not yet assigned | Not reported | [1148448] |
| Pip | asyncssh | pip | Not reported | 2.24.0 | Not reported | GHSA-RW4J-R22C-9GC3 | Not reported |
| Opensuse | python-asyncssh | rpm | leap 16.0 | 2.21.0-bp160.2.1 | Not reported | OPENSUSE-SU-2026:21953-1 | Not reported |
Notes
[trixie] python-asyncssh: Minor issue
OpenFactory catalog packages
[Debian 12 (Bookworm)]
- [python3-asyncssh]Affected
Source package: [python-asyncssh]
Details (4)
2.10.1-2+deb12u2· all · bookwormAffected
nvd · python-asyncssh · debian · bookworm; nvd · python-asyncssh · debian · 12
2.10.1-2+deb12u2· all · bookwormAffected
nvd · python-asyncssh · debian · bookworm; nvd · python-asyncssh · debian · 12
2.10.1-2+deb12u1· all · bookworm-securityAffected
nvd · python-asyncssh · debian · bookworm; nvd · python-asyncssh · debian · 12
2.10.1-2+deb12u1· all · bookworm-securityAffected
nvd · python-asyncssh · debian · bookworm; nvd · python-asyncssh · debian · 12
- [python-asyncssh-doc]Affected
Source package: [python-asyncssh]
Details (4)
2.10.1-2+deb12u2· all · bookwormAffected
nvd · python-asyncssh · debian · bookworm; nvd · python-asyncssh · debian · 12
2.10.1-2+deb12u2· all · bookwormAffected
nvd · python-asyncssh · debian · bookworm; nvd · python-asyncssh · debian · 12
2.10.1-2+deb12u1· all · bookworm-securityAffected
nvd · python-asyncssh · debian · bookworm; nvd · python-asyncssh · debian · 12
2.10.1-2+deb12u1· all · bookworm-securityAffected
nvd · python-asyncssh · debian · bookworm; nvd · python-asyncssh · debian · 12
[Debian 13 (Trixie)]
- [python3-asyncssh]Affected
Source package: [python-asyncssh]
Details (2)
2.20.0-1· all · trixieAffected
nvd · python-asyncssh · debian · 13
2.20.0-1· all · trixieAffected
nvd · python-asyncssh · debian · 13
- [python-asyncssh-doc]Affected
Source package: [python-asyncssh]
Details (2)
2.20.0-1· all · trixieAffected
nvd · python-asyncssh · debian · 13
2.20.0-1· all · trixieAffected
nvd · python-asyncssh · debian · 13
Observed:
References
- [https://ftp.suse.com/pub/projects/security/csaf/opensuse-su-2026_11851-1.json]
- [https://github.com/advisories/GHSA-rw4j-r22c-9gc3]
- [https://nvd.nist.gov/vuln/detail/CVE-2026-62949]
- [https://osv.dev/vulnerability/DEBIAN-CVE-2026-62949]
- [https://osv.dev/vulnerability/openSUSE-SU-2026:21953-1]
- [https://security-tracker.debian.org/tracker/CVE-2026-62949]
- [https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-62949.json]
[Debian Security Tracker] · [FIRST EPSS] · [GitHub Advisory Database] · [National Vulnerability Database (NVD)] · [OSV Package Vulnerability Database] · [Red Hat security advisories and VEX] · [SUSE security advisories and VEX]