# CVE-2026-39849: Pi-hole FTL remote code execution via newline injection in dns.interface configuration

> Remote attackers can execute arbitrary commands on Pi-hole hosts by injecting newlines into the DNS interface configuration, especially when no admin password is set.

- **Severity:** High 8.7 (`CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 5 May 2026
- **Updated:** 8 May 2026
- **Also known as:** GHSA-9cqv-839p-gpq2

## What is CVE-2026-39849?

CVE-2026-39849 is a high-severity command injection vulnerability in pi-hole FTL, published on 5 May 2026. Any signed-in user can exploit it over the network, with no action from the victim.

### Official description

Pi-hole FTL is the core engine of the Pi-hole network-level advertisement and tracker blocker. In versions before 6.6.1, the `dns.interface` configuration field in Pi-hole FTL accepted newline characters without validation, allowing an attacker to inject arbitrary directives into the generated dnsmasq configuration file. On installations with no admin password set (the default for many deployments), the configuration API is fully accessible without credentials, allowing a network-adjacent attacker to inject the payload, enable the built-in DHCP server, and achieve arbitrary command execution on the host the next time any device on the network requests a DHCP lease. The injected value is persisted to /etc/pihole/pihole.toml and survives restarts. The strncpy in the code path limits the total interface field to 31 bytes, but payloads such as wlan0\ndhcp-script=/tmp/p fit within this constraint. The dnsmasq config validation introduced in FTL 6.6 only checks syntactic validity, so valid directives injected via newline pass validation successfully. This issue has been fixed in version 6.6.1.

Weakness: CWE-93 (Improper Neutralization of CRLF Sequences)

## Which versions are affected by CVE-2026-39849?

It affects 1 product.


Products: Pi-Hole Ftldns.

## How do I fix CVE-2026-39849?

No fix has been published for CVE-2026-39849 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-39849 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-39849 exists.

## Other vulnerabilities in pi-hole FTL

- [CVE-2026-35517](https://insights.sbomify.com/CVE-2026-35517/): Pi-hole FTL affected by Remote Code Execution (RCE) via dns.upstreams Newline Injection (high 8.8)
- [CVE-2026-35518](https://insights.sbomify.com/CVE-2026-35518/): Pi-hole FTL affected by Remote Code Execution (RCE) via dns.cnameRecords Newline Injection (high 8.8)
- [CVE-2026-35519](https://insights.sbomify.com/CVE-2026-35519/): Pi-hole FTL affected by Remote Code Execution (RCE) via dns.hostRecord Newline Injection (high 8.8)
- [CVE-2026-35520](https://insights.sbomify.com/CVE-2026-35520/): Pi-hole FTL affected by Remote Code Execution (RCE) via dhcp.leaseTime Newline Injection (high 8.8)
- [CVE-2026-35521](https://insights.sbomify.com/CVE-2026-35521/): Pi-hole FTL affected by Remote Code Execution (RCE) via dhcp.hosts Newline Injection (high 8.8)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-39849 and fix it if it is affected.

What it is: CVE-2026-39849 is a high-severity command injection vulnerability in pi-hole FTL, published on 5 May 2026. Any signed-in user can exploit it over the network, with no action from the victim.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-39849 exists.

Affected product: pi-hole FTL. 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-2026-39849/ (Markdown: https://insights.sbomify.com/CVE-2026-39849/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-39849
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-39849
- OSV: https://osv.dev/vulnerability/CVE-2026-39849

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-39849/
Summaries are generated and may contain mistakes; the official description above is the record.