# CVE-2026-42770: openssl: Issue summary: When EVP_PKEY_derive_set_peer() is called with a DHX (X9.42) peer key, the peer key is not properly ch...

CVE-2026-42770 is fixed in 15 products on 1 platform, first by libssl3t64 3.5.5-1ubuntu3.2, released June 8, 2026. It is not reported as exploited. Patch Radar priority: High.

- Web page: https://patchblox.com/security/cve/CVE-2026-42770
- Priority: High
- CVSS: 9.1 (low)
- EPSS: 0.0050
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Published: Jun 8, 2026

## Description

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.

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Linux | libssl3 Ubuntu 22.04.1 LTS (jammy) | 3.0.2-0ubuntu1.25 | [libssl3 3.0.2-0ubuntu1.25](https://patchblox.com/security/data/fix/linux/ubuntu-jammy-libssl3-3.0.2-0ubuntu1.25.md) | Jun 24, 2026 |
| Linux | libssl3t64 Ubuntu 24.04.5 LTS (noble) | 3.0.13-0ubuntu3.11 | [libssl3t64 3.0.13-0ubuntu3.11](https://patchblox.com/security/data/fix/linux/ubuntu-noble-libssl3t64-3.0.13-0ubuntu3.11.md) | Jun 24, 2026 |
| Linux | libssl3t64 Ubuntu 25.10 (questing) | 3.5.3-1ubuntu3.4 | [libssl3t64 3.5.3-1ubuntu3.4](https://patchblox.com/security/data/fix/linux/ubuntu-questing-libssl3t64-3.5.3-1ubuntu3.4.md) | Jun 24, 2026 |
| Linux | libssl3t64 Ubuntu 26.04.1 LTS (resolute) | 3.5.5-1ubuntu3.2 | [libssl3t64 3.5.5-1ubuntu3.2](https://patchblox.com/security/data/fix/linux/ubuntu-resolute-libssl3t64-3.5.5-1ubuntu3.2.md) | Jun 8, 2026 |
| Linux | openssl Debian 12.15 (bookworm) | 3.0.20-1~deb12u2 | [DEBIAN-CVE-2026-42770](https://patchblox.com/security/data/fix/linux/debian-cve-2026-42770.md) | Jun 24, 2026 |
| Linux | openssl Debian 13.5 (trixie) | 3.5.6-1~deb13u2 | [DEBIAN-CVE-2026-42770](https://patchblox.com/security/data/fix/linux/debian-cve-2026-42770.md) | Jun 24, 2026 |
| Linux | openssl Debian 14 | 3.6.3-1 | [DEBIAN-CVE-2026-42770](https://patchblox.com/security/data/fix/linux/debian-cve-2026-42770.md) | Jun 24, 2026 |
| Linux | openssl RHEL 10 | 3.5.5-4.el10_2 | [RHSA-2026:25237](https://patchblox.com/security/data/fix/linux/rhsa-2026-25237.md) | Jun 24, 2026 |
| Linux | openssl RHEL 9 | 1:3.5.5-4.el9_8 | [RHSA-2026:25239](https://patchblox.com/security/data/fix/linux/rhsa-2026-25239.md) | Jun 24, 2026 |
| Linux | openssl Ubuntu 22.04.1 LTS (jammy) | 3.0.2-0ubuntu1.25 | [openssl 3.0.2-0ubuntu1.25](https://patchblox.com/security/data/fix/linux/ubuntu-jammy-openssl-3.0.2-0ubuntu1.25.md) | Jun 24, 2026 |
| Linux | openssl Ubuntu 24.04.5 LTS (noble) | 3.0.13-0ubuntu3.11 | [openssl 3.0.13-0ubuntu3.11](https://patchblox.com/security/data/fix/linux/ubuntu-noble-openssl-3.0.13-0ubuntu3.11.md) | Jun 24, 2026 |
| Linux | openssl Ubuntu 25.10 (questing) | 3.5.3-1ubuntu3.4 | [openssl 3.5.3-1ubuntu3.4](https://patchblox.com/security/data/fix/linux/ubuntu-questing-openssl-3.5.3-1ubuntu3.4.md) | Jun 24, 2026 |
| Linux | openssl Ubuntu 26.04.1 LTS (resolute) | 3.5.5-1ubuntu3.2 | [openssl 3.5.5-1ubuntu3.2](https://patchblox.com/security/data/fix/linux/ubuntu-resolute-openssl-3.5.5-1ubuntu3.2.md) | Jun 8, 2026 |
| Linux | openssl almalinux 10 | 1:3.5.5-4.el10_2.alma.1 | [ALSA-2026:25237](https://patchblox.com/security/data/fix/linux/alsa-2026-25237.md) | Jun 11, 2026 |
| Linux | openssl almalinux 9 | 1:3.5.5-4.el9_8 | [ALSA-2026:25239](https://patchblox.com/security/data/fix/linux/alsa-2026-25239.md) | Jun 11, 2026 |
| Linux | openssl amzn 2023 | 1:3.5.5-1.amzn2023.0.5 | [ALAS2023-2026-1853](https://patchblox.com/security/data/fix/linux/alas2023-2026-1853.md) | Jun 22, 2026 |
| Linux | openssl ol 10 | 1:3.5.5-5.0.1.el10_2 | [ELSA-2026-25237](https://patchblox.com/security/data/fix/linux/elsa-2026-25237.md) | Jul 28, 2026 |
| Linux | openssl ol 9 | 1:3.5.5-4.0.1.el9_8 | [ELSA-2026-25239](https://patchblox.com/security/data/fix/linux/elsa-2026-25239.md) | Jun 23, 2026 |
| Linux | openssl rocky 10 | 1:3.5.5-4.el10_2 | [RLSA-2026:25237](https://patchblox.com/security/data/fix/linux/rlsa-2026-25237.md) | Jun 13, 2026 |
| Linux | openssl rocky 9 | 1:3.5.5-4.el9_8 | [RLSA-2026:25239](https://patchblox.com/security/data/fix/linux/rlsa-2026-25239.md) | Jun 13, 2026 |
| Linux | openssl-3 opensuse-leap 16.0 | 3.5.0-160000.8.1 | [OPENSUSE-SU-2026:21005-1](https://patchblox.com/security/data/fix/linux/opensuse-su-2026-21005-1.md) | Jun 22, 2026 |
| Linux | openssl-3 sles 15.6 | 3.1.4-150600.5.53.1 | [SUSE-SU-2026:2393-1](https://patchblox.com/security/data/fix/linux/suse-su-2026-2393-1.md) | Jun 15, 2026 |
| Linux | openssl-3 sles 15.7 | 3.2.3-150700.5.36.1 | [SUSE-SU-2026:2648-1](https://patchblox.com/security/data/fix/linux/suse-su-2026-2648-1.md) | Jun 26, 2026 |
| Linux | openssl-3 sles 16.0 | 3.5.0-160000.8.1 | [SUSE-SU-2026:22315-1](https://patchblox.com/security/data/fix/linux/suse-su-2026-22315-1.md) | Jun 22, 2026 |
| Linux | openssl-debuginfo amzn 2023 | 1:3.5.5-1.amzn2023.0.5 | [ALAS2023-2026-1853](https://patchblox.com/security/data/fix/linux/alas2023-2026-1853.md) | Jun 22, 2026 |
| Linux | openssl-debugsource amzn 2023 | 1:3.5.5-1.amzn2023.0.5 | [ALAS2023-2026-1853](https://patchblox.com/security/data/fix/linux/alas2023-2026-1853.md) | Jun 22, 2026 |
| Linux | openssl-devel RHEL 9 | 1:3.5.5-4.el9_8 | [RHSA-2026:25239](https://patchblox.com/security/data/fix/linux/rhsa-2026-25239.md) | Jun 24, 2026 |
| Linux | openssl-devel almalinux 10 | 1:3.5.5-4.el10_2.alma.1 | [ALSA-2026:25237](https://patchblox.com/security/data/fix/linux/alsa-2026-25237.md) | Jun 11, 2026 |
| Linux | openssl-devel almalinux 9 | 1:3.5.5-4.el9_8 | [ALSA-2026:25239](https://patchblox.com/security/data/fix/linux/alsa-2026-25239.md) | Jun 11, 2026 |
| Linux | openssl-devel amzn 2023 | 1:3.5.5-1.amzn2023.0.5 | [ALAS2023-2026-1853](https://patchblox.com/security/data/fix/linux/alas2023-2026-1853.md) | Jun 22, 2026 |
| Linux | openssl-devel ol 10 | 1:3.5.5-5.0.1.el10_2 | [ELSA-2026-25237](https://patchblox.com/security/data/fix/linux/elsa-2026-25237.md) | Jul 28, 2026 |
| Linux | openssl-devel ol 9 | 1:3.5.5-4.0.1.el9_8 | [ELSA-2026-25239](https://patchblox.com/security/data/fix/linux/elsa-2026-25239.md) | Jun 23, 2026 |
| Linux | openssl-fips-provider-latest amzn 2023 | 1:3.5.5-1.amzn2023.0.5 | [ALAS2023-2026-1853](https://patchblox.com/security/data/fix/linux/alas2023-2026-1853.md) | Jun 22, 2026 |
| Linux | openssl-fips-provider-latest-debuginfo amzn 2023 | 1:3.5.5-1.amzn2023.0.5 | [ALAS2023-2026-1853](https://patchblox.com/security/data/fix/linux/alas2023-2026-1853.md) | Jun 22, 2026 |
| Linux | openssl-libs RHEL 9 | 1:3.5.5-4.el9_8 | [RHSA-2026:25239](https://patchblox.com/security/data/fix/linux/rhsa-2026-25239.md) | Jun 24, 2026 |
| Linux | openssl-libs almalinux 10 | 1:3.5.5-4.el10_2.alma.1 | [ALSA-2026:25237](https://patchblox.com/security/data/fix/linux/alsa-2026-25237.md) | Jun 11, 2026 |
| Linux | openssl-libs almalinux 9 | 1:3.5.5-4.el9_8 | [ALSA-2026:25239](https://patchblox.com/security/data/fix/linux/alsa-2026-25239.md) | Jun 11, 2026 |
| Linux | openssl-libs amzn 2023 | 1:3.5.5-1.amzn2023.0.5 | [ALAS2023-2026-1853](https://patchblox.com/security/data/fix/linux/alas2023-2026-1853.md) | Jun 22, 2026 |
| Linux | openssl-libs ol 10 | 1:3.5.5-5.0.1.el10_2 | [ELSA-2026-25237](https://patchblox.com/security/data/fix/linux/elsa-2026-25237.md) | Jul 28, 2026 |
| Linux | openssl-libs ol 9 | 1:3.5.5-4.0.1.el9_8 | [ELSA-2026-25239](https://patchblox.com/security/data/fix/linux/elsa-2026-25239.md) | Jun 23, 2026 |
| Linux | openssl-libs-debuginfo amzn 2023 | 1:3.5.5-1.amzn2023.0.5 | [ALAS2023-2026-1853](https://patchblox.com/security/data/fix/linux/alas2023-2026-1853.md) | Jun 22, 2026 |
| Linux | openssl-perl RHEL 9 | 1:3.5.5-4.el9_8 | [RHSA-2026:25239](https://patchblox.com/security/data/fix/linux/rhsa-2026-25239.md) | Jun 24, 2026 |
| Linux | openssl-perl almalinux 10 | 1:3.5.5-4.el10_2.alma.1 | [ALSA-2026:25237](https://patchblox.com/security/data/fix/linux/alsa-2026-25237.md) | Jun 11, 2026 |
| Linux | openssl-perl almalinux 9 | 1:3.5.5-4.el9_8 | [ALSA-2026:25239](https://patchblox.com/security/data/fix/linux/alsa-2026-25239.md) | Jun 11, 2026 |
| Linux | openssl-perl amzn 2023 | 1:3.5.5-1.amzn2023.0.5 | [ALAS2023-2026-1853](https://patchblox.com/security/data/fix/linux/alas2023-2026-1853.md) | Jun 22, 2026 |
| Linux | openssl-perl ol 10 | 1:3.5.5-5.0.1.el10_2 | [ELSA-2026-25237](https://patchblox.com/security/data/fix/linux/elsa-2026-25237.md) | Jul 28, 2026 |
| Linux | openssl-perl ol 9 | 1:3.5.5-4.0.1.el9_8 | [ELSA-2026-25239](https://patchblox.com/security/data/fix/linux/elsa-2026-25239.md) | Jun 23, 2026 |
| Linux | openssl-provider-legacy Ubuntu 25.10 (questing) | 3.5.3-1ubuntu3.4 | [openssl-provider-legacy 3.5.3-1ubuntu3.4](https://patchblox.com/security/data/fix/linux/ubuntu-questing-openssl-provider-legacy-3.5.3-1ubuntu3.4.md) | Jun 24, 2026 |
| Linux | openssl-provider-legacy Ubuntu 26.04.1 LTS (resolute) | 3.5.5-1ubuntu3.2 | [openssl-provider-legacy 3.5.5-1ubuntu3.2](https://patchblox.com/security/data/fix/linux/ubuntu-resolute-openssl-provider-legacy-3.5.5-1ubuntu3.2.md) | Jun 8, 2026 |
| Linux | openssl-snapsafe-libs amzn 2023 | 1:3.5.5-1.amzn2023.0.5 | [ALAS2023-2026-1853](https://patchblox.com/security/data/fix/linux/alas2023-2026-1853.md) | Jun 22, 2026 |
| Linux | openssl-snapsafe-libs-debuginfo amzn 2023 | 1:3.5.5-1.amzn2023.0.5 | [ALAS2023-2026-1853](https://patchblox.com/security/data/fix/linux/alas2023-2026-1853.md) | Jun 22, 2026 |

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