# CVE-2016-9594: Weak cryptography in curl

> Weak random number generation in libcurl allows attackers to bypass security mechanisms relying on entropy.

- **Severity:** Medium 6.5 (`CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/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:** 23 Apr 2018
- **Updated:** 15 Apr 2026
- **Also known as:** ALPINE-CVE-2016-9594, CLEANSTART-2026-QX18395, CURL-CVE-2016-9594, GHSA-qq6c-xrmh-q72x

## What is CVE-2016-9594?

CVE-2016-9594 is a medium-severity vulnerability in Haxx Curl, published on 23 Apr 2018. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

curl before version 7.52.1 is vulnerable to an uninitialized random in libcurl's internal function that returns a good 32bit random value.  Having a weak or virtually non-existent random value makes the operations that use it vulnerable.

Weakness: CWE-665 (Improper Initialization)

## Which versions are affected by CVE-2016-9594?

It affects 1 product.


Products: Haxx Curl.

## How do I fix CVE-2016-9594?

Upgrade to a fixed version.

## Is CVE-2016-9594 being exploited?

There is no known exploitation of CVE-2016-9594 in the wild and no public exploit code.

## Other vulnerabilities in Haxx Curl

- [CVE-2026-19931](https://insights.sbomify.com/CVE-2026-19931/): Negotiate ambient user conn reuse (critical 9.8)
- [CVE-2026-10536](https://insights.sbomify.com/CVE-2026-10536/): HTTP/2 stream-dependency tree UAF (critical 9.8)
- [CVE-2026-11856](https://insights.sbomify.com/CVE-2026-11856/): cross-origin Digest auth state leak (critical 9.8)
- [CVE-2026-8925](https://insights.sbomify.com/CVE-2026-8925/): SASL double-free (critical 9.8)
- [CVE-2026-9079](https://insights.sbomify.com/CVE-2026-9079/): stale proxy password leak (critical 9.8)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2016-9594 and fix it if it is affected.

What it is: CVE-2016-9594 is a medium-severity vulnerability in Haxx Curl, published on 23 Apr 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-2016-9594 in the wild and no public exploit code.

Affected product: Haxx Curl. 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-2016-9594/ (Markdown: https://insights.sbomify.com/CVE-2016-9594/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2016-9594
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2016-9594
- OSV: https://osv.dev/vulnerability/CVE-2016-9594

---
From sbomify Insights: https://insights.sbomify.com/CVE-2016-9594/
Summaries are generated and may contain mistakes; the official description above is the record.