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CVE-2026-39849

Pi-hole Ftldns vulnerability

8.8 HIGHPublic exploitEPSS 1.00%
  1. Published5 May 2026

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.

CVSS 3.1 breakdown

Attack vectorNetwork
Attack complexityLow
Privileges requiredLow
User interactionNone
ScopeUnchanged
ConfidentialityHigh
IntegrityHigh
AvailabilityHigh
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

Affected products

Pi-hole Ftldns6.6

Remediation

No fixed version is recorded in the NVD data. Check the vendor advisory for the latest guidance.

References

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Frequently asked

Is CVE-2026-39849 being actively exploited?

CVE-2026-39849 is not in the CISA KEV catalog. A public exploit reference exists, so treat it as exploitable. Its EPSS exploit probability is 1.00%.

How severe is CVE-2026-39849?

CVE-2026-39849 has a CVSS 3.1 base score of 8.8, rated high. EPSS estimates a 1.00% probability of exploitation.

Which products are affected by CVE-2026-39849?

Affected products include Pi-hole Ftldns.

How do I fix CVE-2026-39849?

Apply the vendor's patch or advisory guidance, then verify no affected versions remain across your devices.

How Secuno handles this

Secuno correlates vulnerabilities like CVE-2026-39849 against the real software inventory on every managed device, as each hourly inventory arrives. Rather than a static severity, each match is scored in context: exploit availability, EPSS, the asset's exposure, and business criticality decide where it lands in the queue. If an affected version is present anywhere across your portfolio, it surfaces automatically with a prioritised remediation path.

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Data from the NVD, CISA KEV catalog and FIRST EPSS. CVSS 3.1 base score shown where available.