# CVE-2016-8623: Use after free in curl

> A use-after-free flaw in curl's cookie handling allows attackers to disclose sensitive information via concurrent thread access.

- **Severity:** Low 3.3 (`CVSS:3.0/AV:L/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 1 Aug 2018
- **Updated:** 16 Apr 2026
- **Also known as:** ALPINE-CVE-2016-8623, CLEANSTART-2026-HY33416, CURL-CVE-2016-8623, DEBIAN-CVE-2016-8623, GHSA-jfjh-88vc-36cr, UBUNTU-CVE-2016-8623

## What is CVE-2016-8623?

CVE-2016-8623 is a low-severity use after free vulnerability in Haxx Curl, published on 1 Aug 2018. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

A flaw was found in curl before version 7.51.0. The way curl handles cookies permits other threads to trigger a use-after-free leading to information disclosure.

Weakness: CWE-416 (Use After Free)

## Which versions are affected by CVE-2016-8623?

It affects 1 product.


Products: Haxx Curl.

## How do I fix CVE-2016-8623?

Upgrade to a fixed version.

## Is CVE-2016-8623 being exploited?

There is no known exploitation of CVE-2016-8623 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-2016-8623 and fix it if it is affected.

What it is: CVE-2016-8623 is a low-severity use after free vulnerability in Haxx Curl, published on 1 Aug 2018. It can only be exploited from the same machine or local network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2016-8623 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-2016-8623/ (Markdown: https://insights.sbomify.com/CVE-2016-8623/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2016-8623
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2016-8623
- OSV: https://osv.dev/vulnerability/CVE-2016-8623

---
From sbomify Insights: https://insights.sbomify.com/CVE-2016-8623/
Summaries are generated and may contain mistakes; the official description above is the record.