CVE-2026-62949

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{"affected": [{"affectedData": [{"product": "asyncssh", "vendor": "ronf", "versions": [{"status": "affected", "version": "< 2.24.0"}]}], "source": "security-advisories@github.com"}], "cveTags": [], "descriptions": [{"lang": "en", "value": "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", "lastModified": "2026-09-30T17:43:24.057", "metrics": {"cvssMetricV31": [{"cvssData": {"attackComplexity": "LOW", "attackVector": "NETWORK", "availabilityImpact": "HIGH", "baseScore": 6.5, "baseSeverity": "MEDIUM", "confidentialityImpact": "NONE", "integrityImpact": "NONE", "privilegesRequired": "LOW", "scope": "UNCHANGED", "userInteraction": "NONE", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H", "version": "3.1"}, "exploitabilityScore": 2.8, "impactScore": 3.6, "source": "security-advisories@github.com", "type": "Secondary"}], "ssvcV203": [{"source": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "ssvcData": {"id": "CVE-2026-62949", "options": [{"exploitation": "none"}, {"automatable": "no"}, {"technicalImpact": "partial"}], "role": "CISA Coordinator", "timestamp": "2026-09-17T15:01:41.382412Z", "version": "2.0.3"}}]}, "published": "2026-09-16T20:17:26.220", "references": [{"source": "security-advisories@github.com", "url": "https://github.com/ronf/asyncssh/commit/756cbae5350789ce9735f15f704bae9b5a3608b8"}, {"source": "security-advisories@github.com", "url": "https://github.com/ronf/asyncssh/commit/9c354270c009285525e126721e8ed5fbed1f8a67"}, {"source": "security-advisories@github.com", "url": "https://github.com/ronf/asyncssh/releases/tag/v2.24.0"}, {"source": "security-advisories@github.com", "url": "https://github.com/ronf/asyncssh/security/advisories/GHSA-rw4j-r22c-9gc3"}], "sourceIdentifier": "security-advisories@github.com", "vulnStatus": "Awaiting Analysis", "weaknesses": [{"description": [{"lang": "en", "value": "CWE-835"}], "source": "security-advisories@github.com", "type": "Secondary"}]}

{"bugzilla": {"description": "asyncssh: AsyncSSH: Denial of Service via zero-sized SSH packets", "id": "2535643", "url": "https://bugzilla.redhat.com/show_bug.cgi?id=2535643"}, "csaw": false, "cvss3": {"cvss3_base_score": "6.5", "cvss3_scoring_vector": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H", "status": "draft"}, "cwe": "CWE-835", "details": ["A flaw was found in AsyncSSH, a Python package for SSHv2 protocol implementation. A malicious SSH server or an authenticated client can exploit this vulnerability by sending a specially crafted SSH packet with a zero-sized maximum packet size. This can cause the AsyncSSH event loop to freeze, leading to a Denial of Service (DoS) for all current and future connections handled by the process."], "name": "CVE-2026-62949", "package_state": [{"cpe": "cpe:/a:redhat:ceph_storage:7", "fix_state": "Fix deferred", "package_name": "rhceph/rhceph-7-rhel9", "product_name": "Red Hat Ceph Storage 7"}, {"cpe": "cpe:/a:redhat:ceph_storage:8", "fix_state": "Fix deferred", "package_name": "rhceph/rhceph-8-rhel9", "product_name": "Red Hat Ceph Storage 8"}, {"cpe": "cpe:/a:redhat:ceph_storage:9", "fix_state": "Out of support scope", "package_name": "rhceph/rhceph-9-rhel9", "product_name": "Red Hat Ceph Storage 9"}], "public_date": "2026-09-16T20:00:46Z", "references": ["https://www.cve.org/CVERecord?id=CVE-2026-62949\nhttps://nvd.nist.gov/vuln/detail/CVE-2026-62949\nhttps://github.com/ronf/asyncssh/commit/756cbae5350789ce9735f15f704bae9b5a3608b8\nhttps://github.com/ronf/asyncssh/commit/9c354270c009285525e126721e8ed5fbed1f8a67\nhttps://github.com/ronf/asyncssh/releases/tag/v2.24.0\nhttps://github.com/ronf/asyncssh/security/advisories/GHSA-rw4j-r22c-9gc3"], "threat_severity": "Moderate"}

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