CVE-2026-102821

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 2026-09-30. 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 weekElevated

Also known asEUVD-2026-89204 (ENISA EUVD) · GHSA-35g8-35p8-c8fw (GitHub Security Advisories)Source: ENISA EUVD

6.5EG
EchelonGraph verdictPlan a fixRemediate within your standard update timelines (the SSVC decision on this page).
  • CISA's Vulnrichment rates exploitation as PoC; EchelonGraph holds no exploit-code reference for it
CISA-KEV: Not listedEPSS PROB: 0.4%CVSS: 6.5Exploit: No code on recordExposed services: Not assessed

A fix is available — apply it.

Russh is a Rust SSH client and server library. Prior to 0.63.2, an authenticated remote peer can send SSH_MSG_KEXINIT without the required SSH_MSG_KEX_ECDH_INIT and then flood SSH_MSG_CHANNEL_OPEN messages while SessionKexState::InProgress prevents priority_receiver in russh/src/server/session.rs from being drained. The server continues processing network input and enqueues a ChannelOpenReply for each request on an unbounded channel, allowing one connection to grow memory until the process is terminated. This issue is fixed in version 0.63.2.

CVSS v3
6.5
EG Score
6.5MEDIUMmedium confidence
EG Risk
45
EG Risk 45/100

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.
Exploitation40% × 40%
EchelonGraph's fixed weight for EG-KEV Tier 3 (Elevated): a constant, not a probability.
Automatability0% × 15%
CISA's SSVC Automatable value: no (Vulnrichment).
SSVC (CISA's decision table, applied by EchelonGraph): Track at low or medium mission impact; Track* at high (mission-essential systems).
Exploitation public PoC (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
29th
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 low or medium mission impact; Track* at high (mission-essential systems).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 low or medium mission impact; Track* at high (mission-essential systems).

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

Exploitation public PoC (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 29, 2026

Last Modified

September 30, 2026

Advisory Details (3)

Auto-updated Sep 29, 2026
Patch available. Sources: github, github_commit, github_release.
GitHub release Patch Available

v0.63.2

Patch available: Eugeny/russh v0.63.2

https://github.com/Eugeny/russh/releases/tag/v0.63.2
GitHub commit Patch Available

commit a282af361ac9 (Eugeny/russh)

Patch available: Eugeny/russh v0.63.2 (contains commit a282af361ac9)

https://github.com/Eugeny/russh/commit/a282af361ac99bc76b80876d1aae128e89dbf66b
GitHub advisoryMentions a patch (unverified)

Unbounded memory exhaustion via CHANNEL_OPEN flood during a client-stalled rekey · Advisory · Eugeny/russh · GitHub

Affected: v0.63.1; this is a distinct root cause.

https://github.com/Eugeny/russh/security/advisories/GHSA-35g8-35p8-c8fw

Vendor Advisories for CVE-2026-102821(2)

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

Patch Availability(2)

Vendor / EcosystemFix (by version range) / PatchReleasedSource
redhatopenshell-main-0.1.2-0.2.hum12026-10-01redhat
rustrussh @ 0.63.2 (fixes <= 0.63.1)—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

(1 across 1 ecosystem)
crates.io(1)
PackageVulnerable rangeFix by version rangeDependents
russh—
  • every version up to 0.63.2: fixed in 0.63.2
—

Weakness Classification(2)

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

Data Freshness Timeline

(refreshed 10× in last 7d / 55× 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. 2026-11-02 16:43 UTCEPSS rescoreEPSS 0.4% · 29th percentile
  2. 2026-11-01 16:33 UTCEPSS rescoreEPSS 0.4% · 29th percentile
  3. 2026-11-01 08:00 UTCGHSA enrichmentGHSA-35g8-35p8-c8fw · GitHub severity MODERATE · GitHub CVSS 6.5
  4. 2026-11-01 08:00 UTCEG score recompute
  5. 2026-10-31 16:31 UTCEPSS rescoreEPSS 0.4% · 29th percentile
  6. 2026-10-31 12:25 UTCOSV refresh
  7. 2026-10-30 16:33 UTCEPSS rescoreEPSS 0.4% · 29th percentile
  8. 2026-10-29 16:32 UTCEPSS rescoreEPSS 0.4% · 29th percentile
  9. 2026-10-28 16:31 UTCEPSS rescoreEPSS 0.4% · 29th percentile
  10. 2026-10-27 16:31 UTCEPSS rescoreEPSS 0.4% · 29th percentile
  11. 2026-10-26 16:30 UTCEPSS rescoreEPSS 0.4% · 29th percentile
  12. 2026-10-25 16:32 UTCEPSS rescoreEPSS 0.4% · 29th percentile
  13. 2026-10-25 14:56 UTCEG score recompute
  14. 2026-10-24 16:31 UTCEPSS rescoreEPSS 0.3% · 21st percentile
  15. 2026-10-23 16:31 UTCEPSS rescoreEPSS 0.3% · 21st percentile
  16. 2026-10-23 09:28 UTCEG score recompute
  17. 2026-10-23 09:28 UTCVendor advisory
  18. 2026-10-22 16:33 UTCEPSS rescoreEPSS 0.3% · 20th percentile
  19. 2026-10-21 16:31 UTCEPSS rescoreEPSS 0.3% · 20th percentile
  20. 2026-10-20 16:31 UTCEPSS rescoreEPSS 0.3% · 20th percentile
  21. 2026-10-19 16:31 UTCEPSS rescoreEPSS 0.3% · 20th percentile
  22. 2026-10-18 16:31 UTCEPSS rescoreEPSS 0.3% · 20th percentile
  23. 2026-10-18 05:10 UTCEG score recompute
  24. 2026-10-17 16:33 UTCEPSS rescoreEPSS 0.3% · 20th percentile
  25. 2026-10-16 16:40 UTCEPSS rescoreEPSS 0.3% · 20th percentile
Show 43 more
  1. 2026-10-15 16:31 UTCEPSS rescoreEPSS 0.3% · 20th percentile
  2. 2026-10-14 16:31 UTCEPSS rescoreEPSS 0.3% · 20th percentile
  3. 2026-10-13 16:33 UTCEPSS rescoreEPSS 0.3% · 20th percentile
  4. 2026-10-12 16:40 UTCEG score recompute
  5. 2026-10-12 16:33 UTCEPSS rescoreEPSS 0.3% · 20th percentile
  6. 2026-10-11 20:16 UTCEG score recompute
  7. 2026-10-11 18:28 UTCEG score recompute
  8. 2026-10-11 15:01 UTCEG score recompute
  9. 2026-10-11 13:47 UTCEPSS rescoreEPSS 0.3% · 20th percentile
  10. 2026-10-11 07:44 UTCEG score recompute
  11. 2026-10-11 07:44 UTCVendor advisory
  12. 2026-10-10 19:59 UTCEPSS rescoreEPSS 0.3% · 20th percentile
  13. 2026-10-10 06:36 UTCEG score recompute
  14. 2026-10-10 06:36 UTCVendor advisory
  15. 2026-10-09 20:06 UTCEPSS rescoreEPSS 0.3% · 20th percentile
  16. 2026-10-09 05:29 UTCEG score recompute
  17. 2026-10-09 05:29 UTCVendor advisory
  18. 2026-10-08 17:11 UTCEPSS rescoreEPSS 0.3% · 20th percentile
  19. 2026-10-08 04:22 UTCEG score recompute
  20. 2026-10-08 04:22 UTCVendor advisory
  21. 2026-10-07 23:47 UTCEPSS rescoreEPSS 0.3% · 20th percentile
  22. 2026-10-07 03:15 UTCEG score recompute
  23. 2026-10-07 03:15 UTCVendor advisory
  24. 2026-10-06 15:17 UTCEPSS rescoreEPSS 0.3% · 20th percentile
  25. 2026-10-06 02:08 UTCEG score recompute
  26. 2026-10-06 02:08 UTCVendor advisory
  27. 2026-10-05 17:42 UTCEPSS rescoreEPSS 0.3% · 20th percentile
  28. 2026-10-05 00:59 UTCEG score recompute
  29. 2026-10-05 00:59 UTCVendor advisory
  30. 2026-10-04 23:21 UTCEPSS rescoreEPSS 0.3% · 20th percentile
  31. 2026-10-03 23:47 UTCEG score recompute
  32. 2026-10-03 23:47 UTCVendor advisory
  33. 2026-10-03 14:25 UTCEPSS rescoreEPSS 0.3% · 20th percentile
  34. 2026-10-02 22:38 UTCEG score recompute
  35. 2026-10-02 22:38 UTCVendor advisory
  36. 2026-10-01 21:29 UTCEG score recompute
  37. 2026-10-01 19:49 UTCEPSS rescoreEPSS 0.3% · 20th percentile
  38. 2026-09-30 20:23 UTCEG score recompute
  39. 2026-09-30 19:46 UTCEG score recompute
  40. 2026-09-30 15:02 UTCEPSS rescoreEPSS 0.3% · 19th percentile
  41. 2026-09-29 19:20 UTCEG score recompute
  42. 2026-09-29 18:29 UTCEG score recomputeFirst assessed: 6.5 MEDIUM
  43. 2026-09-29 18:28 UTCMITRE cvelistV5first tracked

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Frequently asked(5)

What is CVE-2026-102821?
CVE-2026-102821 is a medium-severity vulnerability; its CVE record was published on September 29, 2026. Russh is a Rust SSH client and server library. Prior to 0.63.2, an authenticated remote peer can send SSH_MSG_KEXINIT without the required SSH_MSG_KEX_ECDH_INIT and then flood SSH_MSG_CHANNEL_OPEN messages while SessionKexState::InProgress prevents priority_receiver in russh/src/server/session.rs…
When was the CVE record for CVE-2026-102821 published?
The CVE record for CVE-2026-102821 was published on September 29, 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-2026-102821 actively exploited?
CVE-2026-102821 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0.4% probability of exploitation in the next 30 days (29th percentile of EPSS-scored CVEs).
What is the CVSS score of CVE-2026-102821?
CVE-2026-102821 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-2026-102821?
A fix for CVE-2026-102821 is available: update to the fixed version the vendor names in its advisory. The vendor advisories EchelonGraph has for CVE-2026-102821 are linked in the Vendor Advisories panel on this page.

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