---
id: "CVE-2026-123125"
kind: "vulnerability"
aliases: ["CVE-2026-123125"]
title: "Symfony Validator: Ip constraint accepts some internal addresses, enabling SSRF"
severity: "medium"
cvss: 6.3
epss: null
exploited: false
status: "open"
category: "package"
products: []
ecosystems: []
tags: ["package", "php", "ssrf", "symfony", "web-apps"]
not_affected_if: ["no-ip-constraint", "no-user-supplied-urls", "static-export"]
published_at: "2026-11-05T16:17:46+00:00"
first_seen_at: "2026-11-05T16:40:02+00:00"
updated_at: "2026-11-05T16:41:41+00:00"
sources: [{"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-123125", "first_seen_at": "2026-11-05T16:40:02+00:00"}]
exploit_sources: []
---

# Symfony Validator: Ip constraint accepts some internal addresses, enabling SSRF

The Symfony Validator's Ip constraint, in its filtered modes, fails to classify shared-space and embedded IPv4 addresses (such as ::ffff:127.0.0.1) as internal, so they pass as public. An attacker who supplies a URL or address that the application then requests can reach internal hosts, a server-side request forgery.

_Summary, check and fix written by a model from the sources; labelled as such._

## How to check

- Run `composer show symfony/validator` and compare the version to the fixed releases.
- Search the codebase for `new Ip(` or `#[Assert\Ip(` used with filtered modes such as `Ip::PRIVATE_NETWORK`, `Ip::PUBLIC_ONLY` or `Ip::ALL_NO_RES`, and check whether it guards outbound requests.

## Fix

- symfony/validator 5.4 series: upgrade to `5.4.56`
- symfony/validator 6.x: upgrade to `6.4.50`
- symfony/validator 7.x: upgrade to `7.4.23`
- symfony/validator 8.x: upgrade to `8.1.11`

## Timeline

- 2026-11-05T16:40:02+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-123125

## Documents

- [advisory] Vendor advisory: github.com https://github.com/symfony/symfony/security/advisories/GHSA-4qpf-57w4-m3wc
- [fix] Patch: github.com https://github.com/symfony/symfony/commit/3bf8ea37fcb402c5ecc502a3f63012df85a7572e

## From the sources

The Symfony Validator component IpValidator incompletely classifies internal addresses in the filtered modes of the Ip constraint, so some internal addresses are accepted as public, which can lead to Server-Side Request Forgery (SSRF) in Symfony versions prior to 5.4.56, 6.x prior to 6.4.50, 7.x prior to 7.4.23, and 8.x prior to 8.1.11.

In these modes, IpValidator relies on the PHP flags FILTER_FLAG_NO_PRIV_RANGE and FILTER_FLAG_NO_RES_RANGE to classify addresses as public, private, or reserved. These flags do not cover shared address space (100.64.0.0/10) or IPv4-mapped, IPv4-compatible, and 6to4 IPv6 addresses, which can embed internal IPv4 addresses. A value such as ::ffff:127.0.0.1 can therefore pass validation even though it points to an internal host.
Applications that rely on the Ip constraint to reject internal addresses, for example before making a server-side request to a user-supplied address, can be exposed to SSRF.

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