---
id: "CVE-2026-121619"
page: "https://infrastack.ai/live/CVE-2026-121619"
kind: "vulnerability"
aliases: ["CVE-2026-121619"]
title: "Symfony: private_ranges trusted proxies let remote clients spoof IP, host and scheme"
severity: "medium"
cvss: 6.3
epss: null
exploited: false
status: "open"
category: "package"
products: []
ecosystems: []
tags: ["package", "php", "reverse-proxy", "self-hosted", "symfony"]
not_affected_if: ["default-config", "no-trusted-proxies", "symfony-6.4"]
published_at: "2026-11-12T19:16:48+00:00"
first_seen_at: "2026-11-12T19:40:13+00:00"
updated_at: "2026-11-12T19:40:53+00:00"
sources: [{"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-121619", "first_seen_at": "2026-11-12T19:40:13+00:00"}]
exploit_sources: []
---

# Symfony: private_ranges trusted proxies let remote clients spoof IP, host and scheme

Link for people: https://infrastack.ai/live/CVE-2026-121619 (this .md is for agents)

Symfony's private_ranges shortcut for trusted proxies includes IPv6 prefixes that embed IPv4 addresses, so a remote client sending from those addresses is treated as a reverse proxy. Its forwarded headers are then honoured, letting an attacker spoof the client IP, host and HTTPS scheme.

_Summary, check and fix written by a model from the sources; labelled as such._

## How to check

- Check the Symfony version with `composer show symfony/http-foundation` and `composer show symfony/framework-bundle`.
- Search the config for `trusted_proxies` and `private_ranges` in framework.yaml, and for calls to `setTrustedProxies` using `private_ranges` or `PRIVATE_SUBNETS`.
- Check whether the app listens on the IPv6 wildcard address without IPV6_V6ONLY, or is reachable over IPv6.

## Fix

- symfony/framework-bundle 7.4.23 and 8.1.11 (7.x and 8.x lines)
- symfony/http-foundation 7.4.23 and 8.1.11

## Timeline

- 2026-11-12T19:40:13+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-121619

## Documents

- [advisory] Maintainer's advisory: github.com https://github.com/symfony/symfony/security/advisories/GHSA-xg2q-4rrq-657q
- [fix] Patch: github.com https://github.com/symfony/symfony/commit/e109aa54d42678e2a72ec148092a8453a67de931

## From the sources

The Symfony FrameworkBundle framework.trusted_proxies option and the HttpFoundation Request::setTrustedProxies() method trust remote clients as reverse proxies when the private_ranges shortcut is used, allowing remote attackers to spoof the client IP address, host and scheme in Symfony FrameworkBundle versions 7.1 prior to 7.4.23 and 8.x prior to 8.1.11, and HttpFoundation versions 7.2 prior to 7.4.23 and 8.x prior to 8.1.11. The private_ranges and PRIVATE_SUBNETS keywords resolved to IpUtils::PRIVATE_SUBNETS, the deny list of NoPrivateNetworkHttpClient, which lists the private and special-purpose prefixes a server must not connect to. Since the fix for CVE-2026-48736 (7.4.13 and 8.0.13), this list also covers the IPv6 prefixes that embed an IPv4 address: IPv4-mapped (::ffff:0:0/96), IPv4-compatible (::/96), 6to4 (2002::/16), Teredo (2001::/32) and NAT64 (64:ff9b::/96). The IPv4-mapped entry has been in the list since the private_ranges shortcut was introduced, in 7.1 for framework.trusted_proxies and in 7.2 for Request::setTrustedProxies(). Over-blocking is safe for a deny list, but when the same entries are used as the allow list of trusted proxies, they trust remote clients. A client whose connection arrives with such a source address is treated as a reverse proxy, and the X-Forwarded-For, X-Forwarded-Host, X-Forwarded-Proto, X-Forwarded-Port and X-Forwarded-Prefix headers it sends are honoured. For example, with Request::setTrustedProxies(['private_ranges'], ...), a request with REMOTE_ADDR set to ::ffff:203.0.113.7 and the headers X-Forwarded-For: 10.0.0.9, X-Forwarded-Host: evil.example.com and X-Forwarded-Proto: https makes getClientIp() return 10.0.0.9, getHost() return evil.example.com and isSecure() return true. Two kinds of deployments are exposed: a server listening on the IPv6 wildcard address without IPV6_V6ONLY reports every IPv4 client in the IPv4-mapped form, so every client is trusted, and a server reachable over IPv6 trusts any client sourcing from 6to4 or Teredo space, which is globally routed, whatever its listener. A spoofed client address defeats IP allow lists, rate limiting and audit logs; a spoofed host poisons the URLs written into password reset and login link e-mails and into shared caches; a spoofed scheme satisfies requires_channel: https over plain HTTP. Symfony 6.4 does not point any trusted proxy setting at IpUtils::PRIVATE_SUBNETS and is not affected by default, but an application that passes that constant to Request::setTrustedProxies() itself could be exposed in the same way on any version. This issue is fixed in 7.4.23 and 8.1.11.

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