Symfony Serializer: Nested Properties Marked #[Ignore] Can Still Be Set

Published as "ObjectNormalizer Dotted-Key Property-Path Traversal Bypasses #[Ignore] on Nested Objects"

medium Symfony Symfony components · Last reviewed Nov 10, 2026

CVE: CVE-2026-122053
GHSA: None
Packagist: PKSA-y18k-qjc6-knrv
Reported: Nov 4, 2026

Lets a client set #[Ignore] properties on nested objects in apps that deserialize input with ObjectNormalizer, such as #[MapRequestPayload].

Affected and fixed versions

In 2 packages: symfony/serializer 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
6.4.9 – 6.4.49	6.4.50	Supported
5.4.41 – 5.4.55	5.4.56	Supported

Show 5 older branches, no longer supported

8.0.0 – 8.0.x	8.1.11
7.1.2 – 7.1.x	7.4.23
7.2.0 – 7.2.x	7.4.23
7.3.0 – 7.3.x	7.4.23
7.0.9 – 7.0.x	7.1.0

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

What this means

A client can set properties you marked with #[Ignore] on nested objects, such as an admin flag on a related object, when your app deserializes their input. Symfony's ObjectNormalizer let a key in the payload reach into nested objects without checking their metadata. The same route can also call a public method of a nested object with a value the attacker picks.

Who is affected

Apps that bind untrusted input to objects with ObjectNormalizer from symfony/serializer (also part of symfony/symfony). That includes controllers using #[MapRequestPayload] or #[MapQueryString], which use ObjectNormalizer by default. It matters when a nested class relies on #[Ignore] to protect a property.

The Symfony advisory says #[Groups] restrictions still hold: the bypass only works when no groups are passed in the context. With OBJECT_TO_POPULATE, used for partial updates, the changed field may be saved to your database.

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. The fix (5.4, 6.4) only accepts a property path when the class metadata declares an attribute with that exact name. Paths you declared on purpose keep working.

Reported by Alexandre Daubois and The PHP Foundation.

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 Serializer: Nested Properties Marked #[Ignore] Can Still Be Set (CVE-2026-122053)
Details: https://phpnews.net/security/symfony/pksa-f5bc-pjy2-fy75

Affected versions, as Composer constraints:
- symfony/serializer, symfony/symfony: >=5.4.41,<5.4.56|>=6.4.9,<6.4.50|>=7.0.9,<7.1.0|>=7.1.2,<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
- 6.4.9 – 6.4.49: update to 6.4.50
- 5.4.41 – 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/pksa-f5bc-pjy2-fy75 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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