CVE-2026-62949

MEDIUMPre-NVD 6.56.5—
EchelonGraph scoreMEDIUM confidence

This medium-severity CVE scores 6.5 under a secondary CVSS source (NVD's own analysis pending). EPSS exploit probability: 0.4%, top 67% of all CVEs by exploit prediction. GitHub Security Advisory data not yet ingested — confidence will rise once GHSA publishes (typical lag: hours to days for open-source ecosystem CVEs; never for infrastructure-only CVEs).

Triggered by: NVD CVSS baseline
Sources: epss, secondary
Trending — 3 sources updated this week
6.5EG
EchelonGraph verdictMonitorLow exploitation likelihood right now — keep watching.
  • Lower severity and no public exploit yet
CISA-KEV: Not listedEPSS PROB: 0%CVSS: 6.5Exploit: None knownExposed: 0

No vendor fix yet — apply a workaround or compensating control (WAF / firewall / segmentation) and watch for a patch.

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.

CVSS v3
6.5
EG Score
6.5(medium)
EG Risk
29(Track)
EG Risk 29/100SSVC: Track

EG Risk is EchelonGraph's 0–100 priority score: it fuses intrinsic severity with real-world exploitation and automatability so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner. Distinct from the 0–10 EG Score (severity).

How it’s computed
Severity65% × 45%
Exploitation0% × 40%
Automatability0% × 15%
Action: Routine — remediate on your standard cadence.
EPSS PROB
0%
EPSS %ILE
33%
KEV
Not listed

Published

September 16, 2026

Last Modified

September 17, 2026

Advisory Details (3)

Auto-updated Sep 16, 2026
Patch available. Sources: github, github_commit.
github_commit

commit 9c354270c009 (ronf/asyncssh)

Fix landed in ronf/asyncssh commit 9c354270c009 — awaiting tagged release

https://github.com/ronf/asyncssh/commit/9c354270c009285525e126721e8ed5fbed1f8a67
github_commit

commit 756cbae53507 (ronf/asyncssh)

Fix landed in ronf/asyncssh commit 756cbae53507 — awaiting tagged release

https://github.com/ronf/asyncssh/commit/756cbae5350789ce9735f15f704bae9b5a3608b8
github Patch Available

asyncio event-loop freeze via SSH maximum packet size = 0 in SSH_MSG_CHANNEL_OPEN / OPEN_CONFIRMATION · Advisory · ronf/asyncssh · GitHub

https://github.com/ronf/asyncssh/security/advisories/GHSA-rw4j-r22c-9gc3

Vendor Advisories for CVE-2026-62949(1)

These vendors published their own advisory mentioning this CVE — often with vendor-specific remediation steps + affected product lists not in NVD.

Affected Packages

(1 across 1 ecosystem)
PyPI(1)
PackageVulnerable rangeFixed inDependents
asyncssh0.8.1 ... 2.9.0 (91 versions)2.24.0—

Weakness Classification(1)

MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.

Data Freshness Timeline

(refreshed 7× in last 7d / 7× in last 30d)

Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. Most recent first.

  1. 2026-09-18 19:28 UTCEPSS rescore
  2. 2026-09-18 18:16 UTCEG score recompute
  3. 2026-09-17 17:59 UTCEG score recompute
  4. 2026-09-17 15:26 UTCEG score recompute
  5. 2026-09-16 20:32 UTCEG score recompute
  6. 2026-09-16 20:09 UTCEG score recompute
  7. 2026-09-16 20:09 UTCMITRE cvelistV5first tracked

Frequently asked(5)

What is CVE-2026-62949?
CVE-2026-62949 is a medium vulnerability published on September 16, 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, processchannelopen and processchannelopenconfirmation in asyncssh/connection.py accept a peer-supplied sendpktsize value of…
When was CVE-2026-62949 disclosed?
CVE-2026-62949 was first published in the National Vulnerability Database on September 16, 2026, with the most recent update on September 17, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-62949 actively exploited?
CVE-2026-62949 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0% probability of exploitation in the next 30 days, which ranks it in the top 67.2% of all scored CVEs.
What is the CVSS score of CVE-2026-62949?
CVE-2026-62949 has a CVSS v3 base score of 6.5 (NVD).
How do I remediate CVE-2026-62949?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-62949, EchelonGraph cross-links them in the Vendor Advisories panel below — those typically contain the canonical remediation steps, fixed version numbers, and any vendor-specific mitigations.

Dependency Blast Radius

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