CVE-2026-62949

MEDIUMPre-NVD 6.56.5
EchelonGraph scoreMEDIUM confidence

“—” beside the score: it is equal to the CVSS score beside it.

Score 6.5 from GitHub Security Advisory (severity: MODERATE) published 2026-09-17. A secondary CVSS source baseline 6.5; sources differ by 0.0.

Triggered by: GitHub Security Advisory CVSS
Sources: EPSS, GitHub Security Advisory, a secondary CVSS source
Trending — 4 sources updated this week

Also known asEUVD-2026-81093 (ENISA EUVD) · GHSA-rw4j-r22c-9gc3 (GitHub Security Advisories) · PYSEC-2026-4026 (OSV.dev)Source: ENISA EUVD

6.5EG
EchelonGraph verdictMonitorRemediate within your standard update timelines (the SSVC decision on this page).
  • Lower severity and no public exploit yet
CISA-KEV: Not listedEPSS PROB: 0.4%CVSS: 6.5Exploit: None knownExposed services: Not assessed

A fix is available — apply it.

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
6.5MEDIUMmedium confidence
EG Risk
29
EG Risk 29/100

EG Risk is EchelonGraph's 0–100 priority score. It fuses impact severity (EG Severity, the CVSS base score, never the KEV-floored or EPSS-lifted EG Score) with real-world exploitation and automatability, under weights EchelonGraph set by hand, so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner.

How it’s computed (value × EchelonGraph’s weight)
Severity65% × 45%
Impact severity (EG Severity): CVSS 6.5 of 10. Never the KEV-floored or EPSS-lifted EG Score.
Exploitation0.4% × 40%
FIRST EPSS: the 30-day exploitation probability when EchelonGraph scored this CVE.
Automatability0% × 15%
CISA's SSVC Automatable value: no (Vulnrichment).
SSVC (CISA's decision table, applied by EchelonGraph): Track at every mission impact level.
Exploitation none (CISA Vulnrichment) · Automatable no (CISA Vulnrichment) · Technical impact partial (CISA Vulnrichment). All three are CISA's SSVC values (Vulnrichment). EchelonGraph applied CISA's decision table to them; CISA publishes SSVC inputs and the table, not a decision for each CVE.
Action: A fix is available. Apply it within your standard update timelines.
EPSS PROB
0.4%
EPSS %ILE
33rd
KEV
Not listed

What the EG score is made of (scorer v4.0: the three questions the 0–10 score mixes, published apart · methodology)

The EG score (6.5): severity, escalated by confirmed exploitation. This CVE's 6.5 is its impact severity (EG Severity), not escalated.

EG Severity
6.5 MEDIUMCVSS-B, impact only: no KEV listing, EPSS or EG-KEV tier raises it.GitHub Security Advisory CVSS
EG Likelihood
0.4% within 30 daysSource: FIRST EPSS (model v2026.06.15, score date 2026-10-31). FIRST's exploitation probability, not an EchelonGraph model.
Confirmed exploitation
None on record (CISA KEV, EG-KEV Tier 1)Reported apart from the likelihood: an observed fact, not a probability.
EG Priority
SSVC Track at medium mission impactTrack at every mission impact level.CISA BOD 26-04: 60 days if the affected system is publicly exposed; Fix on system upgrade if it is not.Each input and its source, and whom BOD 26-04 binds: the SSVC and BOD 26-04 blocks below.

SSVC (CISA's decision table, applied by EchelonGraph)Track at every mission impact level.

A fix is available. Apply it within your standard update timelines.

Exploitation none (CISA Vulnrichment) · Automatable no (CISA Vulnrichment) · Technical impact partial (CISA Vulnrichment). All three are CISA's SSVC values (Vulnrichment). EchelonGraph applied CISA's decision table to them; CISA publishes SSVC inputs and the table, not a decision for each CVE. Mission impact is CISA's Mission & Well-being decision point, and only you can judge it. CISA's table makes it high when Mission Prevalence is Essential — the vulnerable component "directly provides capabilities that constitute at least one MEF for at least one entity" (MEF: mission essential function) — or when Public Well-Being Impact is Irreversible: "multiple fatalities are likely", the cyber-physical system "is likely lost or destroyed", "extreme or serious externalities" are imposed on other parties, or social systems such as elections or the financial grid "are destabilized and potentially collapse". CISA's decision table

BOD 26-04 (CISA's remediation timeline, Table 1)60 days if the affected system is publicly exposed; Fix on system upgrade if it is not.

The score's inputs: In CISA KEV no (CISA's KEV catalog) · Automatable no (CISA Vulnrichment) · Technical impact partial (CISA Vulnrichment). Whether your system is publicly exposed is yours to answer. BOD 26-04 binds US Federal Civilian Executive Branch agencies; for anyone else it is CISA's published timeline, a reference rather than an obligation. The directive · how EchelonGraph applies it

Published

September 16, 2026

Last Modified

September 30, 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 advisoryMentions a patch (unverified)

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.

Patch Availability(1)

Vendor / EcosystemFix (by version range) / PatchReleasedSource
pipasyncssh @ 2.24.0 (fixes <= 2.23.1)—ghsa

Patches are aggregated from vendor advisories (Red Hat, Microsoft, Cisco, GitHub) and package ecosystems (OSV, GHSA). Multiple rows for the same upstream release have been deduplicated.

Affected Packages

(4 across 4 ecosystems)
Debian:12(1)
PackageVulnerable rangeFix by version rangeDependents
python-asyncssh2.10.1-2 ... 2.24.0-2 (17 versions)
  • every version on: no fix on record
—
Debian:13(1)
PackageVulnerable rangeFix by version rangeDependents
python-asyncssh2.20.0-1 ... 2.24.0-2 (8 versions)
  • every version on: no fix on record
—
Debian:14(1)
PackageVulnerable rangeFix by version rangeDependents
python-asyncssh2.20.0-1 ... 2.24.0-2 (8 versions)
  • every version on: no fix on record
—
PyPI(1)
PackageVulnerable rangeFix by version rangeDependents
asyncssh0.8.1 ... 2.9.0 (91 versions)
  • every version up to 2.24.0: fixed in 2.24.0
—

Weakness Classification(1)

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

Data Freshness Timeline

(refreshed 10× in last 7d / 46× in last 30d)

Each row is a time one of our pipelines fetched, updated or re-scored this CVE. 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. An arrow marks a change the record states ("CVSS v3 → 9.1"); EPSS and GHSA rows show the values recorded at that time, not what changed (EPSS values are rounded; hover one for the exact figures). Most recent first.

  1. 2026-11-01 16:35 UTCEPSS rescoreEPSS 0.4% · 33rd percentile
  2. 2026-11-01 07:41 UTCGHSA enrichmentGHSA-rw4j-r22c-9gc3 · GitHub severity MODERATE · GitHub CVSS 6.5
  3. 2026-11-01 07:41 UTCEG score recompute
  4. 2026-10-31 16:33 UTCEPSS rescoreEPSS 0.4% · 33rd percentile
  5. 2026-10-30 16:34 UTCEPSS rescoreEPSS 0.4% · 32nd percentile
  6. 2026-10-30 08:55 UTCOSV refresh
  7. 2026-10-29 16:33 UTCEPSS rescoreEPSS 0.4% · 32nd percentile
  8. 2026-10-28 16:32 UTCEPSS rescoreEPSS 0.4% · 32nd percentile
  9. 2026-10-27 16:32 UTCEPSS rescoreEPSS 0.4% · 32nd percentile
  10. 2026-10-26 16:32 UTCEPSS rescoreEPSS 0.4% · 32nd percentile
  11. 2026-10-25 16:33 UTCEPSS rescoreEPSS 0.4% · 32nd percentile
  12. 2026-10-25 14:13 UTCEG score recompute
  13. 2026-10-24 16:33 UTCEPSS rescoreEPSS 0.4% · 31st percentile
  14. 2026-10-23 16:32 UTCEPSS rescoreEPSS 0.4% · 31st percentile
  15. 2026-10-22 19:51 UTCEG score recompute
  16. 2026-10-22 16:35 UTCEPSS rescoreEPSS 0.4% · 31st percentile
  17. 2026-10-21 16:33 UTCEPSS rescoreEPSS 0.4% · 31st percentile
  18. 2026-10-20 16:33 UTCEPSS rescoreEPSS 0.4% · 31st percentile
  19. 2026-10-19 16:32 UTCEPSS rescoreEPSS 0.4% · 31st percentile
  20. 2026-10-18 16:32 UTCEPSS rescoreEPSS 0.4% · 31st percentile
  21. 2026-10-18 03:23 UTCEG score recompute
  22. 2026-10-17 16:35 UTCEPSS rescoreEPSS 0.4% · 31st percentile
  23. 2026-10-16 16:43 UTCEPSS rescoreEPSS 0.4% · 31st percentile
  24. 2026-10-15 16:32 UTCEPSS rescoreEPSS 0.4% · 31st percentile
  25. 2026-10-14 16:33 UTCEPSS rescoreEPSS 0.4% · 31st percentile
Show 46 more
  1. 2026-10-13 16:34 UTCEPSS rescoreEPSS 0.4% · 31st percentile
  2. 2026-10-12 16:34 UTCEPSS rescoreEPSS 0.4% · 31st percentile
  3. 2026-10-12 15:49 UTCEG score recompute
  4. 2026-10-11 19:33 UTCEG score recompute
  5. 2026-10-11 16:48 UTCEG score recompute
  6. 2026-10-11 14:10 UTCEG score recompute
  7. 2026-10-11 13:49 UTCEPSS rescoreEPSS 0.4% · 30th percentile
  8. 2026-10-10 22:42 UTCEG score recompute
  9. 2026-10-10 20:00 UTCEPSS rescoreEPSS 0.4% · 30th percentile
  10. 2026-10-09 20:48 UTCEG score recompute
  11. 2026-10-09 20:07 UTCEPSS rescoreEPSS 0.4% · 30th percentile
  12. 2026-10-08 20:33 UTCEG score recompute
  13. 2026-10-08 17:13 UTCEPSS rescoreEPSS 0.4% · 30th percentile
  14. 2026-10-07 23:48 UTCEPSS rescoreEPSS 0.4% · 30th percentile
  15. 2026-10-06 19:49 UTCEG score recompute
  16. 2026-10-06 15:18 UTCEPSS rescoreEPSS 0.4% · 30th percentile
  17. 2026-10-05 19:35 UTCEG score recompute
  18. 2026-10-05 17:43 UTCEPSS rescoreEPSS 0.4% · 30th percentile
  19. 2026-10-04 23:22 UTCEPSS rescoreEPSS 0.4% · 30th percentile
  20. 2026-10-03 19:06 UTCEG score recompute
  21. 2026-10-03 14:26 UTCEPSS rescoreEPSS 0.4% · 30th percentile
  22. 2026-10-02 18:48 UTCEG score recompute
  23. 2026-10-02 17:56 UTCEPSS rescoreEPSS 0.4% · 30th percentile
  24. 2026-10-01 19:50 UTCEPSS rescoreEPSS 0.4% · 30th percentile
  25. 2026-09-30 17:49 UTCEG score recompute
  26. 2026-09-30 15:03 UTCEPSS rescoreEPSS 0.4% · 30th percentile
  27. 2026-09-30 00:50 UTCEG score recompute
  28. 2026-09-28 21:14 UTCEG score recompute
  29. 2026-09-28 13:51 UTCEPSS rescoreEPSS 0.4% · 30th percentile
  30. 2026-09-27 20:59 UTCEG score recompute
  31. 2026-09-26 20:45 UTCEG score recompute
  32. 2026-09-26 15:59 UTCEPSS rescoreEPSS 0.5% · 43rd percentile
  33. 2026-09-24 19:47 UTCEG score recompute
  34. 2026-09-23 19:32 UTCEG score recompute
  35. 2026-09-23 17:54 UTCEPSS rescoreEPSS 0.4% · 32nd percentile
  36. 2026-09-22 19:17 UTCEG score recompute
  37. 2026-09-21 19:00 UTCEG score recompute
  38. 2026-09-20 20:16 UTCEPSS rescoreEPSS 0.4% · 32nd percentile
  39. 2026-09-19 18:31 UTCEG score recompute
  40. 2026-09-18 19:28 UTCEPSS rescoreEPSS 0.4% · 32nd percentile
  41. 2026-09-18 18:16 UTCEG score recompute
  42. 2026-09-17 17:59 UTCEG score recompute
  43. 2026-09-17 15:26 UTCEG score recompute
  44. 2026-09-16 20:32 UTCEG score recompute
  45. 2026-09-16 20:09 UTCEG score recomputeFirst assessed: 6.5 MEDIUM
  46. 2026-09-16 20:09 UTCMITRE cvelistV5first tracked

Frequently asked(5)

What is CVE-2026-62949?
CVE-2026-62949 is a medium-severity vulnerability; its CVE record was 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, _process_channel_open and _process_channel_open_confirmation in asyncssh/connection.py accept a peer-supplied send_pktsize…
When was the CVE record for CVE-2026-62949 published?
The CVE record for CVE-2026-62949 was published on September 16, 2026. That is the record's publication date; the vulnerability itself may have been made public earlier. EchelonGraph's copy of the record carries a last-modified date of September 30, 2026; the record at its source may have been updated since.
Is CVE-2026-62949 actively exploited?
CVE-2026-62949 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0.4% probability of exploitation in the next 30 days (33rd percentile of EPSS-scored CVEs).
What is the CVSS score of CVE-2026-62949?
CVE-2026-62949 has a CVSS base score of 6.5 (a secondary CVSS source that NVD displays; NVD's own analysis pending).
How do I remediate CVE-2026-62949?
A fix for CVE-2026-62949 is available: update to the fixed version the vendor names in its advisory. The vendor advisories EchelonGraph has for CVE-2026-62949 are linked in the Vendor Advisories panel on this page.

Dependency Blast Radius

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