# CVE-2021-45841: Auth bypass in n/a

> Attackers can bypass authentication on Terramaster NAS devices by forging session cookies using known MAC addresses and password hashes, allowing unauthorized access.

- **Severity:** High 8.1 (`CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 25 Apr 2022
- **Updated:** 4 Aug 2024
- **Also known as:** GHSA-gmc4-3pqc-993q

## What is CVE-2021-45841?

CVE-2021-45841 is a high-severity authentication bypass vulnerability in n/a, published on 25 Apr 2022. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

In Terramaster F4-210, F2-210 TOS 4.2.X (4.2.15-2107141517), an attacker can self-sign session cookies by knowing the target's MAC address and the user's password hash. Guest users (disabled by default) can be abused using a null/empty hash and allow an unauthenticated attacker to login as guest.

Weakness: CWE-798 (Use of Hard-coded Credentials), CWE-287 (Improper Authentication)

## Which versions are affected by CVE-2021-45841?

It affects 1 product.


Products: Terra-Master Tos.

## How do I fix CVE-2021-45841?

No fix has been published for CVE-2021-45841 yet. Limit exposure of the affected software until one is available.

## Is CVE-2021-45841 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2021-45841 exists.

Public exploit code:

- TerraMaster TOS 4.2.15 or lower - RCE chain from unauthenticated to root via session crafting. (metasploit)

## Other vulnerabilities in n/a

- [CVE-2021-45837](https://insights.sbomify.com/CVE-2021-45837/): Command injection in n/a (critical 9.8)
- [CVE-2021-45840](https://insights.sbomify.com/CVE-2021-45840/): Command injection in n/a (critical 9.8)
- [CVE-2020-15568](https://insights.sbomify.com/CVE-2020-15568/): Code injection in n/a (critical 9.8)
- [CVE-2020-28187](https://insights.sbomify.com/CVE-2020-28187/): Path traversal in n/a (critical 9.8)
- [CVE-2020-28188](https://insights.sbomify.com/CVE-2020-28188/): Command injection in n/a (critical 9.8)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2021-45841 and fix it if it is affected.

What it is: CVE-2021-45841 is a high-severity authentication bypass vulnerability in n/a, published on 25 Apr 2022. 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-2021-45841 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-2021-45841/ (Markdown: https://insights.sbomify.com/CVE-2021-45841/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-45841
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-45841
- OSV: https://osv.dev/vulnerability/CVE-2021-45841

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-45841/
Summaries are generated and may contain mistakes; the official description above is the record.