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CVE-2023-48795 medium CVSS 5.9

Vulnerability in russh (CVE-2023-48795)

Summary

Vulnerability in russh (CVE-2023-48795). Data can be tampered with by attackers. Mitigation: upgrade to 0.40.2 or later.

Original description

The description as published by the source.

Summary

Terrapin is a prefix truncation attack targeting the SSH protocol. More precisely, Terrapin breaks the integrity of SSH's secure channel. By carefully adjusting the sequence numbers during the handshake, an attacker can remove an arbitrary amount of messages sent by the client or server at the beginning of the secure channel without the client or server noticing it.

Mitigations

To mitigate this protocol vulnerability, OpenSSH suggested a so-called "strict kex" which alters the SSH handshake to ensure a Man-in-the-Middle attacker cannot introduce unauthenticated messages as well as convey sequence number manipulation across handshakes.

Warning: To take effect, both the client and server must support this countermeasure.

As a stop-gap measure, peers may also (temporarily) disable the affected algorithms and use unaffected alternatives like AES-GCM instead until patches are available.

Details

The SSH specifications of ChaCha20-Poly1305 (chacha20-poly1305@openssh.com) and Encrypt-then-MAC (*-etm@openssh.com MACs) are vulnerable against an arbitrary prefix truncation attack (a.k.a. Terrapin attack). This allows for an extension negotiation downgrade by stripping the SSH_MSG_EXT_INFO sent after the first message after SSH_MSG_NEWKEYS, downgrading security, and disabling attack countermeasures in some versions of OpenSSH. When targeting Encrypt-then-MAC, this attack requires the use of a CBC cipher to be practically exploitable due to the internal wor…

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-2023-48795 has been found in russh.
Data can be tampered with by attackers. CVSS score: 5.9/10.
What to do: upgrade russh to 0.40.2 or later.
If unsure, ask your IT team or search "russh CVE-2023-48795" on the vendor's site.

CVE-2023-48795 (russh) — CWE-354 / CVSS v3 5.9
Attack vector: remote (network-reachable) / unauthenticated / no user interaction
Patched: 0.40.2 — 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-354) exists in russh.

📍 Affected scope

Check the vendor advisory for the affected versions of russh.

🔥 Severity

Severity: Medium (CVSS 5.9/10). Data can be tampered with by attackers.

🔧 How to fix

Update to 0.40.2.

🛡️ 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 0.40.2

    ステージング環境で 0.40.2 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":"0.40.2"}]}]
pip paramiko
[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"3.4.0"}]}]
go golang.org/x/crypto
[{"type":"SEMVER","events":[{"introduced":"0"},{"fixed":"0.17.0"}]}]
crates.io russh
[{"type":"SEMVER","events":[{"introduced":"0"},{"fixed":"0.40.2"}]}]
PyPI paramiko
[{"type":"ECOSYSTEM","events":[{"introduced":"2.5.0"},{"fixed":"3.4.0"}]}]

Fix status by distribution

Fixed packages published by each distribution for this CVE

References

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