Vulnerability in russh (CVE-2026-102824)
Summary
Vulnerability in russh (CVE-2026-102824). Risk of unauthorized operations or information disclosure. Exploitable via server_dh. Mitigation: upgrade to 0.63.0 or later.
Original description
The description as published by the source.
Vulnerability
The hybrid ML-KEM 768 + X25519 key exchange implementation in russh/src/kex/hybrid_mlkem.rs does not validate that the remote peer's X25519 public key is not the zero point (all-zero 32-byte value). This allows a remote peer to force the X25519 contribution to the combined shared secret to zero, reducing the hybrid KEX to a single-algorithm exchange.
Affected code at HEAD (v0.62.4, commit 0089c89):
Server-side (server_dh, lines 92-93):
let mut c_pk1 = MontgomeryPoint([0; 32]);
c_pk1.0.copy_from_slice(c_pk1_bytes);
// No zero-point check - proceeds to: let k_cl = s_secret * c_pk1;
Client-side (compute_shared_secret, lines 154-155):
let mut s_pk1 = MontgomeryPoint([0; 32]);
s_pk1.0.copy_from_slice(s_pk1_bytes);
// No zero-point check - proceeds to: let k_cl = x25519_secret * s_pk1;
Root Cause
Commit a7fc1eb (2026-07-22, "fix mpint encoding and validate curve25519 keys") added zero-point validation to the standalone Curve25519 KEX in russh/src/kex/curve25519.rs at two locations:
server_dhline 77:if client_pubkey.0 == [0u8; 32] { return Err(crate::Error::Kex); }compute_shared_secretline 122:if remote_pubkey.0 == [0u8; 32] { return Err(crate::Error::Kex); }
The same X25519 scalar multiplication pattern appears in hybrid_mlkem.rs, but the fix was not applied there.
Proof of Concept
A malicious SSH client negotiating mlkem768x25519-sha256 can send a KEX_HYBRID_INIT message containing a valid…
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-2026-102824 has been found in russh.
Attackers can target a specific entry point like server_dh over the network to misuse the product.
Risk of unauthorized operations or information disclosure. CVSS score: 4.3/10.
What to do: upgrade russh to 0.63.0 or later.
If unsure, ask your IT team or search "russh CVE-2026-102824" on the vendor's site.
CVE-2026-102824 (russh) — CWE-327 / CVSS v3 4.3
Attack vector: remote (network-reachable) / no user interaction
Attack surface: server_dh / compute_shared_secret / hybrid_mlkem.rs / curve25519.rs
Patched: 0.63.0 — 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.
A vulnerability (CWE-327) exists in russh. Attackers reach the vulnerable code path via server_dh.
Check the vendor advisory for the affected versions of russh. Attack surface: server_dh / compute_shared_secret / hybrid_mlkem.rs / curve25519.rs.
Severity: Medium (CVSS 4.3/10). Risk of unauthorized operations or information disclosure.
Update to 0.63.0.
Until the patch is applied: disable the affected feature, apply WAF rules, or restrict access via network ACLs.
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
-
1Identify 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。 -
2Apply patch patch
Upgrade russh to 0.63.0ステージング環境で 0.63.0 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。
-
3Post-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
References
- web github.com
- web github.com
- web github.com
- web nvd.nist.gov
- web github.com