# CVE-2021-38751: Open redirect in n/a

> Attackers can manipulate HTTP Host headers to alter webpage links, potentially facilitating man-in-the-middle attacks against Exponent CMS users.

- **Severity:** Medium 4.3 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/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:** No
- **Published:** 16 Aug 2021
- **Updated:** 4 Aug 2024
- **Also known as:** GHSA-mg75-hvvv-r45q

## What is CVE-2021-38751?

CVE-2021-38751 is a medium-severity vulnerability in n/a, published on 16 Aug 2021. 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

A HTTP Host header attack exists in ExponentCMS 2.6 and below in /exponent_constants.php. A modified HTTP header can change links on the webpage to an arbitrary value, leading to a possible attack vector for MITM.

Weakness: CWE-116 (Improper Encoding or Escaping of Output)

## Which versions are affected by CVE-2021-38751?

It affects 1 product.


Products: Exponentcms Exponentcms.

## How do I fix CVE-2021-38751?

No fix has been published for CVE-2021-38751 yet. Limit exposure of the affected software until one is available.

## Is CVE-2021-38751 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2021-38751 exists.

Public exploit code:

- ExponentCMS <= 2.6 - Host Header Injection (nuclei): http/cves/2021/CVE-2021-38751.yaml

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2021-38751 and fix it if it is affected.

What it is: CVE-2021-38751 is a medium-severity vulnerability in n/a, published on 16 Aug 2021. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2021-38751 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-2021-38751/ (Markdown: https://insights.sbomify.com/CVE-2021-38751/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-38751
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-38751
- OSV: https://osv.dev/vulnerability/CVE-2021-38751

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-38751/
Summaries are generated and may contain mistakes; the official description above is the record.