Symfony Validator: Ip Constraint Accepts Some Internal Addresses as Public

Published as "Ip Constraint public/private Modes Accept IPv4-Mapped and IPv4-Compatible IPv6 Addresses: SSRF Filter Bypass"

medium Symfony Symfony components · Last reviewed Nov 10, 2026

CVE: CVE-2026-123125
GHSA: None
Packagist: PKSA-mk2k-pp4j-3cvq
Reported: Nov 4, 2026

Lets internal addresses pass #[Assert\Ip] public or no-private checks, getting past SSRF guards built on the Ip constraint.

Affected and fixed versions

In 2 packages: symfony/symfony and symfony/validator. 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/symfony:^8.1.11
composer require symfony/symfony:^7.4.23
composer require symfony/symfony:^6.4.50
composer require symfony/symfony:^5.4.56

What this means

Internal addresses can pass the Ip validation constraint when you use it to allow only public addresses. If your app uses that check to stop server-side request forgery (SSRF, getting your server to make requests on an attacker's behalf), an attacker can get past it and point your server at internal hosts.

The constraint relied only on PHP's built-in IP range flags, which miss several internal and special ranges and some IPv6 spellings of IPv4 addresses.

Who is affected

Apps on symfony/validator (also part of symfony/symfony) that use #[Assert\Ip] in a filtered mode as a security check: Ip::ALL_ONLY_PUBLIC, Ip::ALL_NO_PRIV, Ip::ALL_NO_RES, or their V4 and V6 forms. The Symfony advisory says the plain V4, V6 and ALL modes do no range filtering at all, so they aren't changed. Results also varied with the PHP version.

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 also rejects every non-public range in the filtered modes.

Some values that passed before are now rejected. For example, NO_PRIV and NO_RES now behave like ONLY_PUBLIC, so 127.0.0.1 fails NO_PRIV.

Reported by zx (Jace).

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 Validator: Ip Constraint Accepts Some Internal Addresses as Public (CVE-2026-123125)
Details: https://phpnews.net/security/symfony/pksa-68kf-8d6f-hdsy

Affected versions, as Composer constraints:
- symfony/symfony, symfony/validator: >=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-68kf-8d6f-hdsy 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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