# CVE-2021-28918: Server-side request forgery in n/a

> Attackers can bypass IP filters to perform SSRF, RFI, and LFI attacks, accessing internal network resources via the netmask npm package.

- **Severity:** Critical 9.1 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/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:** 1 Apr 2021
- **Updated:** 3 Aug 2024

## What is CVE-2021-28918?

CVE-2021-28918 is a critical server-side request forgery vulnerability in n/a, published on 1 Apr 2021. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

Improper input validation of octal strings in netmask npm package v1.0.6 and below allows unauthenticated remote attackers to perform indeterminate SSRF, RFI, and LFI attacks on many of the dependent packages. A remote unauthenticated attacker can bypass packages relying on netmask to filter IPs and reach critical VPN or LAN hosts.

Weakness: CWE-704 (Incorrect Type Conversion or Cast)

## Which versions are affected by CVE-2021-28918?

It affects 1 product.


Products: Netmask Project Netmask.

## How do I fix CVE-2021-28918?

Upgrade to a fixed version.

## Is CVE-2021-28918 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2021-28918 exists.

Public exploit code:

- Netmask NPM Package - Server-Side Request Forgery (nuclei): http/cves/2021/CVE-2021-28918.yaml

## Other vulnerabilities in n/a

- [CVE-2021-29418](https://insights.sbomify.com/CVE-2021-29418/): Security feature bypass in n/a (medium 5.3)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2021-28918 and fix it if it is affected.

What it is: CVE-2021-28918 is a critical server-side request forgery vulnerability in n/a, published on 1 Apr 2021. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2021-28918 exists.

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-2021-28918/ (Markdown: https://insights.sbomify.com/CVE-2021-28918/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-28918
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-28918
- OSV: https://osv.dev/vulnerability/CVE-2021-28918

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-28918/
Summaries are generated and may contain mistakes; the official description above is the record.