Symfony Routing: Host Placeholders Can Bypass Path-Based Access Rules

Published as "CVE-2026-118516: Host Placeholders Can Match the Start of the Path in Compiled URL Matchers, Bypassing Path-Based Access Control"

high Symfony Symfony components · Last reviewed Nov 6, 2026

CVE: CVE-2026-118516
GHSA: None
Packagist: PKSA-y8c5-1b7f-r1gj
Reported: Nov 4, 2026

Lets requests reach controllers that path-based access_control rules protect, in apps with routes that use host placeholders.

Affected and fixed versions

In 2 packages: symfony/routing 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
6.4.0 – 6.4.49	6.4.50	Supported
5.4.0 – 5.4.55	5.4.56	Supported

Show 17 older branches, no longer supported

8.0.0 – 8.0.x	8.1.11
7.0.0 – 7.0.x	7.4.23
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
6.0.0 – 6.0.x	6.4.50
6.1.0 – 6.1.x	6.4.50
6.2.0 – 6.2.x	6.4.50
6.3.0 – 6.3.x	6.4.50
4.1.0 – 4.1.x	5.4.56
4.2.0 – 4.2.x	5.4.56
4.3.0 – 4.3.x	5.4.56
4.4.0 – 4.x	5.4.56
5.0.0 – 5.0.x	5.4.56
5.1.0 – 5.1.x	5.4.56
5.2.0 – 5.2.x	5.4.56
5.3.0 – 5.3.x	5.4.56

Upgrade

Run the line for the branch you are on. 1 other package listed above is affected too; update it the same way.

composer require symfony/routing:^8.1.11
composer require symfony/routing:^7.4.23
composer require symfony/routing:^6.4.50
composer require symfony/routing:^5.4.56

What this means

A request can reach a controller that your path-based access rules are meant to protect, such as an admin page behind access_control, without passing those rules. It works on routes that use a placeholder in their host.

Symfony's compiled URL matcher let a host placeholder swallow the start of the path. The router then picked the protected route, while the access rules checked a different path.

Who is affected

Apps on symfony/routing (also part of symfony/symfony) with routes that set a host containing a placeholder, such as app.{domain}, and protect those routes with path-based rules: access_control entries or a firewall pattern.

The Symfony advisory says framework.trusted_hosts blocks the attack when the placeholder keeps its default requirement. It doesn't help when the placeholder's requirement accepts /, such as .+. Apps without host placeholders aren't affected.

What to do

Update to 5.4.56, 6.4.50, 7.4.23 or 8.1.11. If you're on 8.0, update to 8.1.11. Then clear your cache: the fix changes how routes are compiled, so your app keeps the vulnerable compiled routes until the cache is rebuilt. Until you can update, set framework.trusted_hosts.

Reported by Vincent Cassiau (CyberVanguard).

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 Routing: Host Placeholders Can Bypass Path-Based Access Rules (CVE-2026-118516)
Details: https://phpnews.net/security/symfony/cve-2026-118516

Affected versions, as Composer constraints:
- symfony/routing, symfony/symfony: >=4.1.0,<4.2.0|>=4.2.0,<4.3.0|>=4.3.0,<4.4.0|>=4.4.0,<5.0.0|>=5.0.0,<5.1.0|>=5.1.0,<5.2.0|>=5.2.0,<5.3.0|>=5.3.0,<5.4.0|>=5.4.0,<5.4.56|>=6.0.0,<6.1.0|>=6.1.0,<6.2.0|>=6.2.0,<6.3.0|>=6.3.0,<6.4.0|>=6.4.0,<6.4.50|>=7.0.0,<7.1.0|>=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

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
- 6.4.0 – 6.4.49: update to 6.4.50
- 5.4.0 – 5.4.55: update to 5.4.56

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/cve-2026-118516 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

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