# CVE-2021-46872: Cross-site scripting in n/a

> The Nim language stdlib RST module allows javascript URIs, enabling cross-site scripting attacks in applications using it.

- **Severity:** Medium 6.1 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** A user has to click or open something
- **Fix available:** Yes
- **Published:** 13 Jan 2023
- **Updated:** 7 Apr 2025
- **Also known as:** DEBIAN-CVE-2021-46872, GHSA-6fm4-9v93-v7gg, UBUNTU-CVE-2021-46872

## What is CVE-2021-46872?

CVE-2021-46872 is a medium-severity cross-site scripting vulnerability in n/a, published on 13 Jan 2023. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.

### Official description

An issue was discovered in Nim before 1.6.2. The RST module of the Nim language stdlib, as used in NimForum and other products, permits the javascript: URI scheme and thus can lead to XSS in some applications. (Nim versions 1.6.2 and later are fixed; there may be backports of the fix to some earlier versions. NimForum 2.2.0 is fixed.)

Weakness: CWE-79 (Improper Neutralization of Input During Web Page Generation)

## Which versions are affected by CVE-2021-46872?

It affects 2 products.


Products: Nim-Lang Nim, Nim-Lang Nimforum.

## How do I fix CVE-2021-46872?

Upgrade to a fixed version.

## Is CVE-2021-46872 being exploited?

There is no known exploitation of CVE-2021-46872 in the wild and no public exploit code.

## Other vulnerabilities in n/a

- [CVE-2020-15690](https://insights.sbomify.com/CVE-2020-15690/): Other in n/a (critical 9.8)
- [CVE-2020-15692](https://insights.sbomify.com/CVE-2020-15692/): Command injection in n/a (critical 9.8)
- [CVE-2021-21372](https://insights.sbomify.com/CVE-2021-21372/): Nimble arbitrary code execution for specially crafted package metadata (high 8.3)
- [CVE-2021-21374](https://insights.sbomify.com/CVE-2021-21374/): Nimble fails to validate certificates due to insecure httpClient defaults (high 8.1)
- [CVE-2021-21373](https://insights.sbomify.com/CVE-2021-21373/): Nimble falls back to insecure http url when fetching packages (high 7.5)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2021-46872 and fix it if it is affected.

What it is: CVE-2021-46872 is a medium-severity cross-site scripting vulnerability in n/a, published on 13 Jan 2023. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.
Exploitation: There is no known exploitation of CVE-2021-46872 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-2021-46872/ (Markdown: https://insights.sbomify.com/CVE-2021-46872/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-46872
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-46872
- OSV: https://osv.dev/vulnerability/CVE-2021-46872

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-46872/
Summaries are generated and may contain mistakes; the official description above is the record.