Symfony Config: XmlUtils::parse() Resolves External Entities in Untrusted XML

Published as "XXE (Local File Read) in Config XmlUtils::parse() via validateOnParse = true"

low Symfony Symfony components · Last reviewed Nov 10, 2026

CVE: CVE-2026-123824
GHSA: None
Packagist: PKSA-9myg-zzdn-22rg
Reported: Nov 4, 2026

Can reveal whether server files exist, or leak them through network stream wrappers, in apps that pass untrusted XML to XmlUtils::parse().

Affected and fixed versions

In 2 packages: symfony/config 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 16 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
2.0.0 – 2.x	5.4.56
3.0.0 – 3.x	5.4.56
4.0.0 – 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/config:^8.1.11
composer require symfony/config:^7.4.23
composer require symfony/config:^6.4.50
composer require symfony/config:^5.4.56

What this means

Symfony's XmlUtils::parse(), in the Config component, resolves external entities (references inside an XML document that point to other files) before it rejects the document. If your app passes untrusted XML to it, an attacker can learn whether files exist on your server, tie it up reading a large or slow file, and in some setups read files.

This is the same flaw CVE-2026-45071 fixed in the DomCrawler component. The copy in the Config component was missed at the time. See the Symfony advisory and the fix.

Who is affected

Only apps that call Symfony\Component\Config\Util\XmlUtils::parse() themselves with XML from users or another untrusted source.

Symfony's own callers are safe. The XML loaders of DependencyInjection, Routing, Validator and Serializer, XliffFileLoader and QtFileLoader read your own config and translation files. The Loco, Crowdin and Lokalise translation providers pass it documents from the service you configured.

For an exposed app, how much leaks depends on its stream wrappers. File contents can only leave the server if the app has registered a network-capable stream wrapper, such as s3://. Symfony rates the issue low because so few apps reach this code with untrusted input.

What to do

Update symfony/config (or symfony/symfony) to 5.4.56, 6.4.50, 7.4.23 or 8.1.11, depending on your branch. The fix removes a single line that turned on DTD validation, so parsing of valid config files doesn't change.

Reported by Prithiv Kumaravel (ProjectDiscovery) and Björn Meyer of Shopware AG.

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 Config: XmlUtils::parse() Resolves External Entities in Untrusted XML (CVE-2026-123824)
Details: https://phpnews.net/security/symfony/pksa-j458-vmkj-zs4x

Affected versions, as Composer constraints:
- symfony/config, symfony/symfony: >=2.0.0,<3.0.0|>=3.0.0,<4.0.0|>=4.0.0,<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/pksa-j458-vmkj-zs4x 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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