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CVE-2026-48107 medium CVSS 6.5

Vulnerability in russh (CVE-2026-48107)

Summary

Vulnerability in russh (CVE-2026-48107). Risk of unauthorized operations or information disclosure. Exploitable via russh. Mitigation: upgrade to 0.61.0 or later.

Original description

The description as published by the source.

Summary

In the russh client keyboard-interactive authentication path, a malicious SSH server could send a USERAUTH_INFO_REQUEST with an attacker-controlled prompt count, and the client would use that raw count directly in Vec::with_capacity(...) before validating that enough prompt data was actually present in the packet.

This is a client-side denial-of-service / resource-exhaustion issue on the keyboard-interactive auth path.

Details

The vulnerable code path is in:

  • russh/src/client/encrypted.rs

When the client is in CurrentRequest::KeyboardInteractive state and receives SSH_MSG_USERAUTH_INFO_REQUEST, it parses:

  1. name
  2. instructions
  3. language tag
  4. n_prompts

Before the fix, the code then did:

let n_prompts = map_err!(u32::decode(&mut r))?;
let mut prompts = Vec::with_capacity(n_prompts.try_into().unwrap_or(0));

That means a malicious server could advertise an enormous n_prompts value even if the packet contained no prompt bodies at all.

The fix rejects inconsistent prompt counts before allocating:

let n_prompts = map_err!(u32::decode(&mut r))?;
let max_prompts = r.remaining_len() / 5;
let n_prompts = n_prompts as usize;
if n_prompts > max_prompts {
    return Err(crate::Error::Inconsistent.into());
}
let mut prompts = Vec::with_capacity(n_prompts);

Each prompt needs at least 4 bytes of string length plus 1 byte of echo flag, so remaining_len() / 5 is a safe upper bound. If the declared count exceeds wh…

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-2026-48107 has been found in russh.
Attackers can target a specific entry point like russh over the network to misuse the product.
Risk of unauthorized operations or information disclosure. CVSS score: 6.5/10.
What to do: upgrade russh to 0.61.0 or later.
If unsure, ask your IT team or search "russh CVE-2026-48107" on the vendor's site.

CVE-2026-48107 (russh) — CWE-20 / CVSS v3 6.5
Attack vector: remote (network-reachable) / unauthenticated
Attack surface: russh / USERAUTH_INFO_REQUEST / SSH_MSG_USERAUTH_INFO_REQUEST / name
Patched: 0.61.0 — 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 russh without authentication.

📍 Affected scope

Check the vendor advisory for the affected versions of russh. Attack surface: russh / USERAUTH_INFO_REQUEST / SSH_MSG_USERAUTH_INFO_REQUEST / name.

🔥 Severity

Severity: Medium (CVSS 6.5/10). Risk of unauthorized operations or information disclosure.

🔧 How to fix

Update to 0.61.0.

🛡️ 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 0.61.0

    ステージング環境で 0.61.0 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":"0.61.0"}]}]
crates.io russh
[{"type":"SEMVER","events":[{"introduced":"0.37.0"},{"fixed":"0.61.0"}]}]

Fix status by distribution

Fixed packages published by each distribution for this CVE

References

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