# CVE-2018-0733: Incorrect CRYPTO_memcmp on HP-UX PA-RISC

> An implementation bug in OpenSSL on HP-UX PA-RISC weakens constant-time comparison, allowing attackers to forge authenticated messages with fewer attempts than expected.

- **Severity:** Medium 5.9 (`CVSS:3.0/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 27 Mar 2018
- **Updated:** 16 Sep 2024
- **Also known as:** ALPINE-CVE-2018-0733, DEBIAN-CVE-2018-0733, GHSA-j66x-3v7r-hj5f

## What is CVE-2018-0733?

CVE-2018-0733 is a medium-severity vulnerability in Openssl Openssl, published on 27 Mar 2018. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

Because of an implementation bug the PA-RISC CRYPTO_memcmp function is effectively reduced to only comparing the least significant bit of each byte. This allows an attacker to forge messages that would be considered as authenticated in an amount of tries lower than that guaranteed by the security claims of the scheme. The module can only be compiled by the HP-UX assembler, so that only HP-UX PA-RISC targets are affected. Fixed in OpenSSL 1.1.0h (Affected 1.1.0-1.1.0g).

## Which versions are affected by CVE-2018-0733?

It affects 1 product.


Products: Openssl Openssl.

## How do I fix CVE-2018-0733?

Upgrade to a fixed version.

## Is CVE-2018-0733 being exploited?

There is no known exploitation of CVE-2018-0733 in the wild and no public exploit code.

## Other vulnerabilities in Openssl Openssl

- [CVE-2009-3245](https://insights.sbomify.com/CVE-2009-3245/): Null dereference in n/a (critical 10.0)
- [CVE-2006-3738](https://insights.sbomify.com/CVE-2006-3738/): Memory corruption in n/a (critical 10.0)
- [CVE-2026-63073](https://insights.sbomify.com/CVE-2026-63073/): Untrusted Sender DN Used as Format String in CMP Response Validation (critical 9.8)
- [CVE-2016-6309](https://insights.sbomify.com/CVE-2016-6309/): Use after free in n/a (critical 9.8)
- [CVE-2016-0799](https://insights.sbomify.com/CVE-2016-0799/): Integer overflow in n/a (critical 9.8)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2018-0733 and fix it if it is affected.

What it is: CVE-2018-0733 is a medium-severity vulnerability in Openssl Openssl, published on 27 Mar 2018. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2018-0733 in the wild and no public exploit code.

Affected product: Openssl Openssl. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2018-0733/ (Markdown: https://insights.sbomify.com/CVE-2018-0733/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2018-0733
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2018-0733
- OSV: https://osv.dev/vulnerability/CVE-2018-0733

---
From sbomify Insights: https://insights.sbomify.com/CVE-2018-0733/
Summaries are generated and may contain mistakes; the official description above is the record.