# CVE-2020-35591: Auth bypass in n/a

> Attackers can hijack user sessions by injecting cookies before login, gaining unauthorized access to Pi-hole admin accounts.

- **Severity:** Medium 5.4 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/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:** No
- **Published:** 18 Feb 2021
- **Updated:** 4 Aug 2024
- **Also known as:** GHSA-fg2g-p9qq-jw38

## What is CVE-2020-35591?

CVE-2020-35591 is a medium-severity authentication bypass vulnerability in n/a, published on 18 Feb 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

Pi-hole 5.0, 5.1, and 5.1.1 allows Session Fixation. The application does not generate a new session cookie after the user is logged in. A malicious user is able to create a new session cookie value and inject it to a victim. After the victim logs in, the injected cookie becomes valid, giving the attacker access to the user's account through the active session.

Weakness: CWE-384 (Session Fixation)

## Which versions are affected by CVE-2020-35591?

It affects 1 product.


Products: Pi-Hole Pi-Hole.

## How do I fix CVE-2020-35591?

No fix has been published for CVE-2020-35591 yet. Limit exposure of the affected software until one is available.

## Is CVE-2020-35591 being exploited?

There is no known exploitation of CVE-2020-35591 in the wild and no public exploit code.

## Other vulnerabilities in n/a

- [CVE-2020-8816](https://insights.sbomify.com/CVE-2020-8816/): Pi-Hole AdminLTE Remote Code Execution (critical 9.1, exploited in the wild)
- [CVE-2025-34087](https://insights.sbomify.com/CVE-2025-34087/): Pi-Hole AdminLTE Whitelist (now 'Web Allowlist') Remote Command Execution (critical 9.0)
- [CVE-2026-50130](https://insights.sbomify.com/CVE-2026-50130/): Pi-hole: Local privilege escalation from `pihole` user to root via `/etc/pihole/logrotate` (high 8.8)
- [CVE-2020-11108](https://insights.sbomify.com/CVE-2020-11108/): File upload in n/a (high 8.8)
- [CVE-2019-13051](https://insights.sbomify.com/CVE-2019-13051/): Pi-Hole 4.3 allows Command Injection. (high 8.8)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2020-35591 and fix it if it is affected.

What it is: CVE-2020-35591 is a medium-severity authentication bypass vulnerability in n/a, published on 18 Feb 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: There is no known exploitation of CVE-2020-35591 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-2020-35591/ (Markdown: https://insights.sbomify.com/CVE-2020-35591/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2020-35591
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2020-35591
- OSV: https://osv.dev/vulnerability/CVE-2020-35591

---
From sbomify Insights: https://insights.sbomify.com/CVE-2020-35591/
Summaries are generated and may contain mistakes; the official description above is the record.