# CVE-2016-6309: Use after free in n/a

> Remote attackers can cause denial of service or execute arbitrary code via crafted TLS sessions due to a use-after-free flaw in OpenSSL.

- **Severity:** Critical 9.8 (`CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 26 Sep 2016
- **Updated:** 6 Aug 2024
- **Also known as:** GHSA-5qvw-r534-xcm4

## What is CVE-2016-6309?

CVE-2016-6309 is a critical use after free vulnerability in Openssl Openssl, published on 26 Sep 2016. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

statem/statem.c in OpenSSL 1.1.0a does not consider memory-block movement after a realloc call, which allows remote attackers to cause a denial of service (use-after-free) or possibly execute arbitrary code via a crafted TLS session.

Weakness: CWE-416 (Use After Free)

## Which versions are affected by CVE-2016-6309?

It affects 1 product.


Products: Openssl Openssl.

## How do I fix CVE-2016-6309?

Apply the vendor's patch.

## Is CVE-2016-6309 being exploited?

There is no known exploitation of CVE-2016-6309 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-2016-0799](https://insights.sbomify.com/CVE-2016-0799/): Integer overflow in n/a (critical 9.8)
- [CVE-2016-2842](https://insights.sbomify.com/CVE-2016-2842/): Memory corruption in n/a (critical 9.8)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2016-6309 and fix it if it is affected.

What it is: CVE-2016-6309 is a critical use after free vulnerability in Openssl Openssl, published on 26 Sep 2016. 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-2016-6309 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-2016-6309/ (Markdown: https://insights.sbomify.com/CVE-2016-6309/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2016-6309
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2016-6309
- OSV: https://osv.dev/vulnerability/CVE-2016-6309

---
From sbomify Insights: https://insights.sbomify.com/CVE-2016-6309/
Summaries are generated and may contain mistakes; the official description above is the record.