---
schema_version: '1.0'
id: security-20260705-56c620
url: https://osv.dev/vulnerability/DEBIAN-CVE-2026-42770
url_hash: 56c620160d5f4a2ec15c6e515547747f96ec27de9f9d46eb36e45bd663b99bb3
canonical_url: https://osv.dev/vulnerability/DEBIAN-CVE-2026-42770
source: osv:debian
category: security/os
category_raw: cve/os
region: null
tags:
- cve
- DEBIAN-CVE-2026-42770
- severity:CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N
- openssl
- Debian
lang: en
published_at: '2026-06-09T17:17:08Z'
fetched_at: '2026-07-05T15:34:34Z'
updated_at: '2026-07-21T06:56:19Z'
status: published
content_hash: 71bcbc5ff30e78fe40a644b6c13e2dcd96e367160efc5c788e8d02a18df61247
content_changed_at: '2026-07-21T06:55:47.561667Z'
license_note: full
summary: 'Issue summary: When EVP_PKEY_derive_set_peer() is called with a DHX (X9.42)
  peer key, the peer key is not properly checked for the subgroup membership.  Impact
  summary: A malicious peer which presents an X9.42 key carrying the victim''s p and
  g parameters, a forged q = r (a small '
summary_source: rss
summary_en: 'Issue summary: When EVP_PKEY_derive_set_peer() is called with a DHX (X9.42)
  peer key, the peer key is not properly checked for the subgroup membership.  Impact
  summary: A malicious peer which presents an X9.42 key carrying the victim''s p and
  g parameters, a forged q = r (a small '
entities: []
related_auto: []
title: DEBIAN-CVE-2026-42770 — openssl
---

# DEBIAN-CVE-2026-42770 — openssl

## TL;DR
Issue summary: When EVP_PKEY_derive_set_peer() is called with a DHX (X9.42) peer key, the peer key is not properly checked for the subgroup membership.  Impact summary: A malicious peer which presents an X9.42 key carrying the victim's p and g parameters, a forged q = r (a small 

## Key Points
- cve / DEBIAN-CVE-2026-42770 / severity:CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N / openssl / Debian

## Details
**Severity:** CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N
**Advisory:** DEBIAN-CVE-2026-42770

**Affected (your watchlist):**
- `Debian:openssl` 3.0.11-1~deb12u2 → no fixed version listed [rpi]

**Details:**
Issue summary: When EVP_PKEY_derive_set_peer() is called with a DHX (X9.42) peer key, the peer key is not properly checked for the subgroup membership.  Impact summary: A malicious peer which presents an X9.42 key carrying the victim's p and g parameters, a forged q = r (a small prime factor of the cofactor (p−1)/q_local), and a public value Y of order r can recover the victim's private key after a small number of key exchange attempts.  When EVP_PKEY_derive_set_peer() is called with a DHX (X9.42) peer key, the subgroup membership check Y^q ≡ 1 (mod p) is performed using the peer's own q parameter, not the local key's q. The peer's domain parameters are then matched against the domain parameters of the private key, but the value of q is not compared.  A malicious peer who presents an X9.42 key carrying the victim's p, g, a forged q = r (a small prime factor of the cofactor), and a public value Y of order r passes all checks. The shared secret then takes only r distinct values, leaking priv mod r. Repeating for each small-prime factor of the cofactor and combining via CRT recovers the full private key (Lim–Lee / small-subgroup-confinement attack).  The realistic attack surface is narrow: principally CMP deployments with long-lived RA/CA DHX keys and bespoke enterprise or government applications using X9.42 DHX static keys with interactive protocols and therefore this issue was assigned Low severity.  The FIPS modules in 4.0, 3.6, 3.5, 3.4, 3.1.2 and 3.0 are affected by this issue.

**References:**
- https://security-tracker.debian.org/tracker/CVE-2026-42770

_Data: OSV.dev (upstream: debian) — https://osv.dev/vulnerability/DEBIAN-CVE-2026-42770_

## Source
元記事: [DEBIAN-CVE-2026-42770 — openssl](https://osv.dev/vulnerability/DEBIAN-CVE-2026-42770) — published 2026-06-09T17:17:08Z