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CVE-2026-102823 high CVSS 7.5

Vulnerability in russh (CVE-2026-102823)

Summary

Vulnerability in russh (CVE-2026-102823). Data can be tampered with by attackers. Exploitable via Handler. Mitigation: upgrade to 0.63.1 or later.

Original description

The description as published by the source.

Summary

CVE-2026-68930 was fixed by adding Session::is_established_channel() in russh/src/server/encrypted.rs, which gates every channel-scoped SERVER-side message (CHANNEL_REQUEST, CHANNEL_DATA, CHANNEL_EOF, CHANNEL_CLOSE, CHANNEL_WINDOW_ADJUST, CHANNEL_EXTENDED_DATA) on enc.channels.get(&channel).is_some_and(|c| c.confirmed) before invoking any Handler callback. The identical validation was never added to the CLIENT side (russh/src/client/encrypted.rs), which processes channel-scoped messages sent by the SSH SERVER once the client has authenticated.

Details

In client_read_authenticated (russh/src/client/encrypted.rs, ~lines 431-757), for CHANNEL_DATA, CHANNEL_EXTENDED_DATA, CHANNEL_EOF, CHANNEL_CLOSE, CHANNEL_OPEN_FAILURE, CHANNEL_SUCCESS, CHANNEL_FAILURE, and the CHANNEL_REQUEST sub-types exit-status/exit-signal/xon-xoff, the code only optionally forwards the event to the internal per-channel mpsc sender via if let Some(chan) = self.channels.get(&channel_num) { ... } (a no-op if the channel is unknown), but then unconditionally calls the corresponding public Handler trait method (client.data(...), client.exit_status(...), client.channel_close(...), client.channel_success(...), etc.) regardless of whether channel_num corresponds to any channel the client ever opened or that was ever confirmed. Only CHANNEL_OPEN_CONFIRMATION (closes the connection with Error::Inconsistent if unknown) and CHANNEL_WINDOW_ADJUST (returns early with `Ok…

Source: NIST National Vulnerability Database NVD GitHub Advisory

Auto-generated summary

Assembled by SecPulse from the source data (CVSS, CWE, affected versions) using templates — no AI involved. Check the original description and references below for exact details.

A vulnerability tracked as CVE-2026-102823 has been found in russh.
Attackers can target a specific entry point like Handler over the network to misuse the product.
Data can be tampered with by attackers. CVSS score: 7.5/10.
What to do: upgrade russh to 0.63.1 or later.
If unsure, ask your IT team or search "russh CVE-2026-102823" on the vendor's site.

CVE-2026-102823 (russh) — CWE-20 / CVSS v3 7.5
Attack vector: remote (network-reachable) / unauthenticated / no user interaction
Attack surface: Handler / client_read_authenticated / channel_num / WrongChannel
Patched: 0.63.1 — apply immediately
Plan: 1) Audit SBOM/dependencies, 2) Stage→prod upgrade, 3) Add WAF/proxy monitoring on affected endpoints, 4) Hunt IOCs in logs.
Refs: see the GHSA / vendor advisory / patched release linked on this page.

❓ What is the problem

A vulnerability (CWE-20) exists in russh. Attackers reach the vulnerable code path via Handler without authentication.

📍 Affected scope

Check the vendor advisory for the affected versions of russh. Attack surface: Handler / client_read_authenticated / channel_num / WrongChannel.

🔥 Severity

Severity: High (CVSS 7.5/10). Data can be tampered with by attackers.

🔧 How to fix

Update to 0.63.1.

🛡️ Workaround

Until the patch is applied: disable the affected feature, apply WAF rules, or restrict access via network ACLs.

🔍 Detection

Search webserver/proxy logs for unusual request patterns matching this CVE's known IOCs. Run grep -r 'russh' . against your dependency files (package-lock.json, requirements.txt, go.sum) to find affected services.

Response actions

Concrete steps and command examples for SOC/SRE teams to execute in order

  1. 1
    Identify exposure identify 
    grep -r 'russh' . | grep -v node_modules

    リポジトリと本番環境の依存ファイル (package-lock.json / requirements.txt / go.sum / Gemfile.lock 等) で russh を grep し、稼働しているサービス・バージョンを把握する。

  2. 2
    Apply patch patch 
    Upgrade russh to 0.63.1

    ステージング環境で 0.63.1 に上げて回帰テスト → 本番反映。回帰テストはアプリの主要ハッピーパスを含めること。

  3. 3
    Post-deployment verification verify 
    Confirm patched version is live in production

    パッチ適用後、ステージングで PoC または同等の悪用パターンを再現して脆弱性が閉じたことを確認。本番ではアクセスログ・WAF でアラート再発が無いか継続監視。

Affected packages

rust russh
[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"0.63.1"}]}]

References

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