Symfony: private_ranges Trusted Proxies Setting Trusts Some Remote Clients

Published as "The "private_ranges" Trusted Proxies Shortcut Trusts Clients Presenting an IPv4-Mapped, 6to4, Teredo or NAT64 Address as Reverse Proxies"

medium Symfony Symfony components · Last reviewed Nov 6, 2026

CVE: No CVE assigned
GHSA: None
Packagist: PKSA-jvt1-tggb-8w72
Reported: Nov 4, 2026

Lets some IPv6 clients pass as trusted proxies and set X-Forwarded headers in apps that use trusted_proxies: private_ranges.

Affected and fixed versions

In 3 packages: symfony/framework-bundle, symfony/http-foundation and symfony/symfony. Find the row for the version you run, and update to the release next to it.

If you run	Update to	Support
8.1.0 – 8.1.10	8.1.11	Supported
7.4.0 – 7.4.22	7.4.23	Supported

Show 4 older branches, no longer supported

8.0.0 – 8.0.x	8.1.11
7.1.0 – 7.1.x	7.4.23
7.2.0 – 7.2.x	7.4.23
7.3.0 – 7.3.x	7.4.23

Upgrade

Run the line for the branch you are on. 2 other packages listed above are affected too; update them the same way.

composer require symfony/framework-bundle:^8.1.11
composer require symfony/framework-bundle:^7.4.23

What this means

Some remote clients can pass as one of your trusted reverse proxies. They can then set X-Forwarded-* headers that your app believes. That lets them fake their IP address and get past IP allow lists, rate limits and logs. They can also change the host used in password reset and login link emails, or pass as HTTPS over plain HTTP.

Who is affected

Apps on symfony/http-foundation 7.2 and later, or symfony/framework-bundle 7.1 and later (also part of symfony/symfony), that set framework.trusted_proxies: private_ranges, or pass private_ranges or PRIVATE_SUBNETS to Request::setTrustedProxies(). The shortcut also covered some IPv6 address ranges that remote clients can use.

The Symfony advisory names two exposed setups. A server listening on all IPv6 addresses without IPV6_V6ONLY reports every IPv4 client in IPv6 form, so it trusts every client. A server reachable over IPv6 trusts clients from 6to4 or Teredo addresses. Symfony 6.4 doesn't use this list by default, but an app that passes IpUtils::PRIVATE_SUBNETS to setTrustedProxies() itself is exposed on any version.

What to do

Update to 7.4.23 or 8.1.11. If you're on 8.0, update to 8.1.11. The fix gives trusted proxies their own list, IpUtils::PRIVATE_RANGES, which 6.4.50 also adds. If you pass IpUtils::PRIVATE_SUBNETS yourself, switch to IpUtils::PRIVATE_RANGES. If a proxy lives in a documentation or reserved range, list it explicitly.

Reported by Ivan Tse.

Check your app with an agent

Paste this into a coding agent that can read your project, such as Claude Code, Codex or Amp. It checks your composer.lock against the versions above and tells you what to update, without changing anything.

Check whether the PHP project you have access to is affected by this security advisory, and tell me what to update. Do a read-only check: don't edit files, don't run composer update or composer require, and don't try to reproduce the flaw.

Advisory: Symfony: private_ranges Trusted Proxies Setting Trusts Some Remote Clients (PKSA-NXJS-S6HN-VB6M)
Details: https://phpnews.net/security/symfony/pksa-nxjs-s6hn-vb6m

Affected versions, as Composer constraints:
- symfony/framework-bundle, symfony/symfony: >=7.1.0,<7.2.0|>=7.2.0,<7.3.0|>=7.3.0,<7.4.0|>=7.4.0,<7.4.23|>=8.0.0,<8.1.0|>=8.1.0,<8.1.11
- symfony/http-foundation: >=7.2.0,<7.3.0|>=7.3.0,<7.4.0|>=7.4.0,<7.4.23|>=8.0.0,<8.1.0|>=8.1.0,<8.1.11

Fixed releases on branches that still get security fixes:
- 8.1.0 – 8.1.10: update to 8.1.11
- 7.4.0 – 7.4.22: update to 7.4.23

1. Find every composer.lock in the project outside vendor/ (a monorepo can have one per app) and read the installed version of each package above. Packages installed as dependencies of other packages count too.
2. Compare each installed version with its constraint: "|" separates alternative ranges, and "," means both bounds apply.
3. For each affected install, read "What this means" at https://phpnews.net/security/symfony/pksa-nxjs-s6hn-vb6m and check whether the project meets the conditions it describes (a feature in use, a config value, a driver). Say which conditions you could check and which you couldn't.
4. Report a table: lock file | package | installed version | affected (yes, no or unknown) | conditions met (yes, no or unknown) | update to | evidence. For each affected package, give the command that would fix it, without running it: composer update <package> --with-dependencies when it is only installed as a dependency of another package, or composer require with the fixed version when composer.json requires it directly. If the installed version is on a branch with no fixed release listed, say it needs a move to a newer branch.

Sources

The project's advisory →

← All Symfony advisories