CVE-2026-102821

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: 0.3% (20th percentile of EPSS-scored CVEs). 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 — Patch released this weekElevated
6.5EG
EchelonGraph verdictMonitorLow exploitation likelihood right now — keep watching.
  • Lower severity and no public exploit yet
CISA-KEV: Not listedEPSS PROB: 0.3%CVSS: 6.5Exploit: Elevated riskExposed 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 45/100CISA SSVC

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%
Exploitation40% × 40%
Automatability0% × 15%
CISA SSVC: Track at low or medium mission impact; Track* at high (mission-essential systems).
Action: A fix is available. Apply it within your standard update timelines.
EPSS PROB
0.3%
EPSS %ILE
20th
KEV
Not listed

CISA SSVCTrack 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). Mission impact is CISA's Mission & Well-being decision point, and only you can judge it: high means the affected system is essential to your organisation's mission, or its compromise could cause irreversible harm to people. CISA's decision table

Published

September 29, 2026

Last Modified

September 30, 2026

Advisory Details (3)

Auto-updated Sep 29, 2026
🔬 Proof of concept available. 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 Patch Available🟡 PoC Available

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(1)

Vendor / EcosystemFixed in / PatchReleasedSource
redhatopenshell-main-0.1.2-0.2.hum12026-10-01redhat

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 rangeFixed inDependents
russh—0.63.2—

Weakness Classification(2)

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

Data Freshness Timeline

(refreshed 13× in last 7d / 13× 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. 2026-10-03 23:47 UTCEG score recompute
  2. 2026-10-03 23:47 UTCVendor advisory
  3. 2026-10-03 14:25 UTCEPSS rescore
  4. 2026-10-02 22:38 UTCEG score recompute
  5. 2026-10-02 22:38 UTCVendor advisory
  6. 2026-10-01 21:29 UTCEG score recompute
  7. 2026-10-01 19:49 UTCEPSS rescore
  8. 2026-09-30 20:23 UTCEG score recompute
  9. 2026-09-30 19:46 UTCEG score recompute
  10. 2026-09-30 15:02 UTCEPSS rescore
  11. 2026-09-29 19:20 UTCEG score recompute
  12. 2026-09-29 18:29 UTCEG score recompute
  13. 2026-09-29 18:28 UTCMITRE cvelistV5first tracked

Related CVEs(same product + same vendor + same CWE)

Frequently asked(5)

What is CVE-2026-102821?
CVE-2026-102821 is a medium vulnerability 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 SSHMSGKEXINIT without the required SSHMSGKEXECDHINIT and then flood SSHMSGCHANNELOPEN messages while SessionKexState::InProgress prevents priorityreceiver in russh/src/server/session.rs from being…
When was CVE-2026-102821 disclosed?
CVE-2026-102821 was first published on September 29, 2026, with the most recent update on September 30, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-102821 actively exploited?
CVE-2026-102821 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0.3% probability of exploitation in the next 30 days (20th 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.

Dependency Blast Radius

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