# CVE-2016-5361: Denial of service in n/a

> Remote attackers can cause denial of service via traffic amplification using spoofed UDP packets in libreswan IPsec implementation.

- **Severity:** High 7.5 (`CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/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:** 16 Jun 2016
- **Updated:** 6 Aug 2024
- **Also known as:** GHSA-pvgh-6wjg-x887, RHSA-2016:2603

## What is CVE-2016-5361?

CVE-2016-5361 is a high-severity denial of service vulnerability in n/a, published on 16 Jun 2016. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

programs/pluto/ikev1.c in libreswan before 3.17 retransmits in initial-responder states, which allows remote attackers to cause a denial of service (traffic amplification) via a spoofed UDP packet. NOTE: the original behavior complies with the IKEv1 protocol, but has a required security update from the libreswan vendor; as of 2016-06-10, it is expected that several other IKEv1 implementations will have vendor-required security updates, with separate CVE IDs assigned to each.

Weakness: CWE-20 (Improper Input Validation)

## Which versions are affected by CVE-2016-5361?

It affects 1 product.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `libreswan` | Red Hat:enterprise_linux:7::client | All versions | 0:3.15-8.el7 |
| `libreswan-debuginfo` | Red Hat:enterprise_linux:7::client | All versions | 0:3.15-8.el7 |
| `libreswan` | Red Hat:enterprise_linux:7::server | All versions | 0:3.15-8.el7 |
| `libreswan-debuginfo` | Red Hat:enterprise_linux:7::server | All versions | 0:3.15-8.el7 |
| `libreswan` | Red Hat:enterprise_linux:7::workstation | All versions | 0:3.15-8.el7 |
| `libreswan-debuginfo` | Red Hat:enterprise_linux:7::workstation | All versions | 0:3.15-8.el7 |

Products: Libreswan Libreswan.

## How do I fix CVE-2016-5361?

Upgrade to a fixed version.

## Is CVE-2016-5361 being exploited?

There is no known exploitation of CVE-2016-5361 in the wild and no public exploit code.

## Other vulnerabilities in n/a

- [CVE-2013-7283](https://insights.sbomify.com/CVE-2013-7283/): Race condition in n/a (critical 9.3)
- [CVE-2026-12413](https://insights.sbomify.com/CVE-2026-12413/): IKEv2 Denial of Service via malformed fragmentation (high 7.5)
- [CVE-2026-50721](https://insights.sbomify.com/CVE-2026-50721/): IKEv1 Denial of Service via RSA-SHA1 (PKCS#1 Version 1.5 Encrypted) authentication payload (high 7.5)
- [CVE-2026-50722](https://insights.sbomify.com/CVE-2026-50722/): IKEv2 Denial of Service via RSA-SHA1 (PKCS#1 RSASSA-PKCS1-v1_5) authentication payload (high 7.5)
- [CVE-2023-30570](https://insights.sbomify.com/CVE-2023-30570/): Denial of service in n/a (high 7.5)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2016-5361 and fix it if it is affected.

What it is: CVE-2016-5361 is a high-severity denial of service vulnerability in n/a, published on 16 Jun 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-2016-5361 in the wild and no public exploit code.

Affected product: n/a. 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-2016-5361/ (Markdown: https://insights.sbomify.com/CVE-2016-5361/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2016-5361
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2016-5361
- OSV: https://osv.dev/vulnerability/CVE-2016-5361

---
From sbomify Insights: https://insights.sbomify.com/CVE-2016-5361/
Summaries are generated and may contain mistakes; the official description above is the record.