CVE-2018-0732 Client DoS due to large DH parameter

High 7.5 Published 12 Jun 2018 Updated 8 Oct 2026

A malicious server can cause a client hang and denial of service by sending a large DH parameter during TLS handshake.

Exploited in the wild: Not known
Login needed: Not needed
Attackable: Over the internet
Victim action needed: Not needed
Fix: Available

What is CVE-2018-0732?

CVE-2018-0732 is a high-severity denial of service vulnerability in Canonical Ubuntu Linux, published on 12 Jun 2018. An attacker can exploit it over the internet without logging in, with no action from the victim.

Official description

During key agreement in a TLS handshake using a DH(E) based ciphersuite a malicious server can send a very large prime value to the client. This will cause the client to spend an unreasonably long period of time generating a key for this prime resulting in a hang until the client has finished. This could be exploited in a Denial Of Service attack. Fixed in OpenSSL 1.1.0i-dev (Affected 1.1.0-1.1.0h). Fixed in OpenSSL 1.0.2p-dev (Affected 1.0.2-1.0.2o).

Weakness: CWE-320

Which versions are affected by CVE-2018-0732?

It affects 4 products.

Linux distribution packages (22)

`openssl` SUSE:Enterprise Storage 4	All versions	`1.0.2j-60.30.1`
`openssl` SUSE:Linux Enterprise Desktop 12 SP3	All versions	`1.0.2j-60.30.1`
`openssl` SUSE:Linux Enterprise Module for Basesystem 15	All versions	`1.1.0i-3.3.1`
`openssl-1_1` SUSE:Linux Enterprise Module for Basesystem 15	All versions	`1.1.0h-4.3.1`
`openssl-1_1` SUSE:Linux Enterprise Module for Basesystem 15	All versions	`1.1.0i-4.9.2`
`openssl-1_0_0` SUSE:Linux Enterprise Module for Legacy 15	All versions	`1.0.2n-3.3.1`
`openssl` SUSE:Linux Enterprise Point of Sale 11 SP3	All versions	`0.9.8j-0.106.12.1`
`openssl` SUSE:Linux Enterprise Server 11 SP3-LTSS	All versions	`0.9.8j-0.106.12.1`
`openssl` SUSE:Linux Enterprise Server 11 SP3-TERADATA	All versions	`0.9.8j-0.106.12.1`
`openssl` SUSE:Linux Enterprise Server 11 SP4	All versions	`0.9.8j-0.106.12.1`
`openssl` SUSE:Linux Enterprise Server 12 SP1-LTSS	All versions	`1.0.1i-54.14.1`
`openssl` SUSE:Linux Enterprise Server 12 SP2-BCL	All versions	`1.0.2j-60.30.1`
`openssl` SUSE:Linux Enterprise Server 12 SP2-LTSS	All versions	`1.0.2j-60.30.1`
`openssl` SUSE:Linux Enterprise Server 12 SP3	All versions	`1.0.2j-60.30.1`
`openssl` SUSE:Linux Enterprise Server for SAP Applications 11 SP4	All versions	`0.9.8j-0.106.12.1`
`openssl` SUSE:Linux Enterprise Server for SAP Applications 12 SP1	All versions	`1.0.1i-54.14.1`
`openssl` SUSE:Linux Enterprise Server for SAP Applications 12 SP2	All versions	`1.0.2j-60.30.1`
`openssl` SUSE:Linux Enterprise Server for SAP Applications 12 SP3	All versions	`1.0.2j-60.30.1`
`openssl` SUSE:Linux Enterprise Software Development Kit 11 SP4	All versions	`0.9.8j-0.106.12.1`
`openssl` SUSE:Linux Enterprise Software Development Kit 12 SP3	All versions	`1.0.2j-60.30.1`
`openssl` SUSE:OpenStack Cloud 7	All versions	`1.0.2j-60.30.1`
`openssl` SUSE:Studio Onsite 1.3	All versions	`0.9.8j-0.106.12.1`

Products include Canonical Ubuntu Linux, Debian Debian Linux, Nodejs Node.js, Openssl Openssl.

How do I fix CVE-2018-0732?

Upgrade to a fixed version.

Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.

Is CVE-2018-0732 being exploited?

There is no known exploitation of CVE-2018-0732 in the wild and no public exploit code.

All Canonical Ubuntu Linux vulnerabilities

Sources

Also known as ALPINE-CVE-2018-0732, DEBIAN-CVE-2018-0732, GHSA-497c-86pp-222m, SUSE-SU-2018:1887-1, SUSE-SU-2018:1887-2, SUSE-SU-2018:1968-1 and 5 more.