# CVE-2021-23518: Prototype Pollution

> Prototype pollution in cached-path-relative allows attackers to manipulate object prototypes, potentially leading to code execution or security bypasses.

- **Severity:** High 7.3 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:L/E:P`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 21 Jan 2022
- **Updated:** 16 Sep 2024
- **Also known as:** DEBIAN-CVE-2021-23518, GHSA-wg6g-ppvx-927h, UBUNTU-CVE-2021-23518

## What is CVE-2021-23518?

CVE-2021-23518 is a high-severity vulnerability in Debian Debian Linux, published on 21 Jan 2022. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

The package cached-path-relative before 1.1.0 are vulnerable to Prototype Pollution via the cache variable that is set as {} instead of Object.create(null) in the cachedPathRelative function, which allows access to the parent prototype properties when the object is used to create the cached relative path. When using the origin path as __proto__, the attribute of the object is accessed instead of a path. **Note:** This vulnerability derives from an incomplete fix in https://security.snyk.io/vuln/SNYK-JS-CACHEDPATHRELATIVE-72573

Weakness: CWE-1321 (Improperly Controlled Modification of Object Prototype Attributes)

## Which versions are affected by CVE-2021-23518?

2 open source packages ship an affected version, including cached-path-relative. It affects 2 products.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `cached-path-relative` | npm | All versions | 1.1.0 |
| `cached-path-relative` | npm | All versions | 1.1.0 |

Products: Cached-Path-Relative Project Cached-Path-Relative, Debian Debian Linux.

## How do I fix CVE-2021-23518?

Upgrade cached-path-relative to 1.1.0 or later.

## Is CVE-2021-23518 being exploited?

There is no known exploitation of CVE-2021-23518 in the wild and no public exploit code.

## Other vulnerabilities in Debian Debian Linux

- [CVE-2018-16472](https://insights.sbomify.com/CVE-2018-16472/): Prototype Pollution in cached-path-relative (high 7.5)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2021-23518 and fix it if it is affected.

What it is: CVE-2021-23518 is a high-severity vulnerability in Debian Debian Linux, published on 21 Jan 2022. 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-2021-23518 in the wild and no public exploit code.

Affected packages and fixed versions:
- cached-path-relative (npm): affected all versions; fixed in 1.1.0
- cached-path-relative (npm): affected all versions; fixed in 1.1.0

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-2021-23518/ (Markdown: https://insights.sbomify.com/CVE-2021-23518/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-23518
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-23518
- OSV: https://osv.dev/vulnerability/CVE-2021-23518

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-23518/
Summaries are generated and may contain mistakes; the official description above is the record.