CVE-2026-42770

描述

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, and 3.0 are affected by this issue.

如何修補 CVE-2026-42770

要修補 CVE-2026-42770,請將受影響套件升級到下列已修補版本。

• —升級至 3.5.7-r0 或更新版本
• —未列出修補版本

CVE-2026-42770 正在被利用嗎?

目前沒有被利用訊號。CVE-2026-42770 既不在 CISA KEV 也沒有最新的 EPSS 分數。

受影響套件(2)

• from 0, < 3.5.7-r0
• from 0

CVSS 分數

參考連結(2)

• ADVISORYsecurity.alpinelinux.org/vuln/CVE-2026-42770
• ADVISORYsecurity-tracker.debian.org/tracker/CVE-2026-42770