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.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- None listed
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
Which versions are affected by CVE-2026-39849?
It affects 1 product.
Products include 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.
Upgrade, and pass arguments to programs as a list instead of through a shell. More about Command injection.
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 Pi-hole FTL affected by Remote Code Execution (RCE) via dns.upstreams Newline Injection
- CVE-2026-35518 Pi-hole FTL affected by Remote Code Execution (RCE) via dns.cnameRecords Newline Injection
- CVE-2026-35519 Pi-hole FTL affected by Remote Code Execution (RCE) via dns.hostRecord Newline Injection
- CVE-2026-35520 Pi-hole FTL affected by Remote Code Execution (RCE) via dhcp.leaseTime Newline Injection
- CVE-2026-35521 Pi-hole FTL affected by Remote Code Execution (RCE) via dhcp.hosts Newline Injection
Sources
Also known as GHSA-9cqv-839p-gpq2.