# CVE-2017-16118: Regular Expression Denial of Service in forwarded

> Attackers can cause a denial of service in Express.js applications by sending specially crafted X-Forwarded-For headers to the forwarded module.

- **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:** 7 Jun 2018
- **Updated:** 17 Sep 2024
- **Also known as:** AZL-44496, CLSA-2026-1773706635, GHSA-mpcf-4gmh-23w8

## What is CVE-2017-16118?

CVE-2017-16118 is a high-severity denial of service vulnerability in HackerOne forwarded node module, published on 7 Jun 2018. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

The forwarded module is used by the Express.js framework to handle the X-Forwarded-For header. It is vulnerable to a regular expression denial of service when it's passed specially crafted input to parse. This causes the event loop to be blocked causing a denial of service condition.

Weakness: CWE-400 (Uncontrolled Resource Consumption)

## Which versions are affected by CVE-2017-16118?

2 open source packages ship an affected version, including forwarded. It affects 1 product.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `forwarded` | npm | All versions | 0.1.2 |
| `forwarded` | npm | All versions | 0.1.2 |

Products: Forwarded Project Forwarded.

## How do I fix CVE-2017-16118?

Upgrade forwarded to 0.1.2 or later.

## Is CVE-2017-16118 being exploited?

There is no known exploitation of CVE-2017-16118 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2017-16118 and fix it if it is affected.

What it is: CVE-2017-16118 is a high-severity denial of service vulnerability in HackerOne forwarded node module, published on 7 Jun 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-2017-16118 in the wild and no public exploit code.

Affected packages and fixed versions:
- forwarded (npm): affected all versions; fixed in 0.1.2
- forwarded (npm): affected all versions; fixed in 0.1.2

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-2017-16118/ (Markdown: https://insights.sbomify.com/CVE-2017-16118/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2017-16118
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2017-16118
- OSV: https://osv.dev/vulnerability/CVE-2017-16118

---
From sbomify Insights: https://insights.sbomify.com/CVE-2017-16118/
Summaries are generated and may contain mistakes; the official description above is the record.