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Authorization bypass: CLI API sessions can import Teleporter archives and modify configuration

Moderate
PromoFaux published GHSA-r7g8-3fj7-m5qq Apr 3, 2026

Package

pi-hole/ftl

Affected versions

>= 6.0, <= 6.5

Patched versions

6.6

Description

Summary

Pi-hole FTL supports a CLI password feature (webserver.api.cli_pw) that creates “CLI” API sessions intended to be read-only for configuration changes. While /api/config correctly blocks
CLI sessions from mutating configuration, /api/teleporter allowed Teleporter imports for CLI sessions, enabling a CLI-scoped session to overwrite configuration via a Teleporter archive
(authorization bypass).

Details

  • CLI sessions are flagged via session->cli (set when authenticating with the CLI password).
  • /api/config blocks CLI sessions by returning HTTP 403 when api->session->cli is true.
  • /api/teleporter did not perform the same check before processing an uploaded Teleporter archive (e.g., ZIP imports can overwrite etc/pihole/pihole.toml; legacy Teleporter TAR.GZ
    imports can restore additional config files).
  • Expected behavior: Teleporter import should be restricted to fully privileged sessions, not CLI sessions.

PoC (local lab)

Prereqs: API password set; CLI password feature enabled (webserver.api.cli_pw=true / FTLCONF_webserver_api_cli_pw=true).

  1. Obtain the CLI password (in a lab it is stored at /etc/pihole/cli_pw) and authenticate to get a sid:
  • POST /api/auth with the CLI password
  1. Confirm CLI sessions are blocked from config changes (expected behavior):
  • Try any config-changing request to /api/config and observe HTTP 403 forbidden
  1. Demonstrate the bypass via Teleporter import:
  • Download a Teleporter archive: GET /api/teleporter
  • Import it back using the same CLI session: POST /api/teleporter with the archive as multipart form field file
  • Observe the import succeeds (and triggers a restart) despite being a CLI session

Impact

An attacker who obtains CLI-scoped API credentials can modify Pi-hole configuration through the Teleporter import endpoint, bypassing intended authorization restrictions for CLI sessions.
This can be used to change settings (e.g., disable blocking, alter upstream DNS, change DHCP settings), impacting integrity/availability.

Suggested fix

Add the same CLI-session restriction used by /api/config to /api/teleporter (reject when api->session->cli is true).

Severity

Moderate

CVSS overall score

This score calculates overall vulnerability severity from 0 to 10 and is based on the Common Vulnerability Scoring System (CVSS).
/ 10

CVSS v3 base metrics

Attack vector
Local
Attack complexity
Low
Privileges required
Low
User interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
High
Availability
Low

CVSS v3 base metrics

Attack vector: More severe the more the remote (logically and physically) an attacker can be in order to exploit the vulnerability.
Attack complexity: More severe for the least complex attacks.
Privileges required: More severe if no privileges are required.
User interaction: More severe when no user interaction is required.
Scope: More severe when a scope change occurs, e.g. one vulnerable component impacts resources in components beyond its security scope.
Confidentiality: More severe when loss of data confidentiality is highest, measuring the level of data access available to an unauthorized user.
Integrity: More severe when loss of data integrity is the highest, measuring the consequence of data modification possible by an unauthorized user.
Availability: More severe when the loss of impacted component availability is highest.
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:L

CVE ID

CVE-2026-35491

Weaknesses

Incorrect Authorization

The product performs an authorization check when an actor attempts to access a resource or perform an action, but it does not correctly perform the check. Learn more on MITRE.

Credits