---
id: CVE-2026-48736
aliases:
  - GHSA-38cx-cq6f-5755
title: >-
  Symfony: IpUtils::PRIVATE_SUBNETS Omits IPv6 Transition Forms (6to4, NAT64,
  Teredo, IPv4-compatible): SSRF Bypass in NoPrivateNetworkHttpClient
summary: >-
  Symfony: IpUtils::PRIVATE_SUBNETS Omits IPv6 Transition Forms (6to4, NAT64,
  Teredo, IPv4-compatible): SSRF Bypass in NoPrivateNetworkHttpClient
severity: medium
cwe:
  - CWE-184
  - CWE-918
vendor: symfony
product: symfony/http-client
ecosystem: composer
affected:
  - 'symfony/http-client >= 5.4.0, < 5.4.53'
  - 'symfony/http-foundation >= 6.4.0, < 6.4.41'
  - 'symfony/http-foundation >= 7.0.0, < 7.4.13'
  - 'symfony/http-foundation >= 8.0.0, < 8.0.13'
  - 'symfony/symfony >= 5.4.0, < 5.4.53'
  - 'symfony/symfony >= 6.4.0, < 6.4.41'
  - 'symfony/symfony >= 7.0.0, < 7.4.13'
  - 'symfony/symfony >= 8.0.0, < 8.0.13'
patched:
  - symfony/http-client 5.4.53
  - symfony/http-foundation 6.4.41
  - symfony/http-foundation 7.4.13
  - symfony/http-foundation 8.0.13
  - symfony/symfony 5.4.53
  - symfony/symfony 6.4.41
  - symfony/symfony 7.4.13
  - symfony/symfony 8.0.13
published: '2026-06-15'
updated: '2026-06-15'
source: GHSA
sourceUrl: 'https://github.com/advisories/GHSA-38cx-cq6f-5755'
references:
  - url: 'https://github.com/symfony/symfony/security/advisories/GHSA-38cx-cq6f-5755'
  - url: >-
      https://github.com/symfony/symfony/commit/82765368cf74177c36613575182f168a2eb765b2
  - url: >-
      https://github.com/symfony/symfony/commit/85b831555be8ea1f43bf01078afe87bc4c92f65e
  - url: >-
      https://github.com/FriendsOfPHP/security-advisories/blob/master/symfony/http-client/CVE-2026-48736.yaml
  - url: >-
      https://github.com/FriendsOfPHP/security-advisories/blob/master/symfony/http-foundation/CVE-2026-48736.yaml
  - url: >-
      https://github.com/FriendsOfPHP/security-advisories/blob/master/symfony/symfony/CVE-2026-48736.yaml
  - url: 'https://symfony.com/cve-2026-48736'
  - url: 'https://github.com/advisories/GHSA-38cx-cq6f-5755'
tags:
  - ghsa
  - composer
ingestedAt: '2026-07-07T15:41:58.734Z'
epss: 0.0057
epssPercentile: 0.4598
---

## Overview

### Description

`Symfony\Component\HttpClient\NoPrivateNetworkHttpClient` is documented as a decorator that blocks requests to private networks by default. The list of blocked subnets (`Symfony\Component\HttpFoundation\IpUtils::PRIVATE_SUBNETS` on 6.4+, a private constant in `NoPrivateNetworkHttpClient` on 5.4) enumerates RFC1918, loopback, link-local and IPv4-mapped IPv6 (`::ffff:0:0/96`) prefixes, but omits the remaining IPv6 transition forms that can embed a private IPv4 destination: 6to4 (`2002::/16`, RFC 3056), Teredo (`2001::/32`, RFC 4380), NAT64 (`64:ff9b::/96`, RFC 6052 and `64:ff9b:1::/48`, RFC 8215) and IPv4-compatible IPv6 (`::/96`, RFC 4291 §2.5.5.1).

`IpUtils::checkIp6()` is a pure bitwise CIDR comparison against the constants list and never extracts the embedded IPv4, so an attacker who can supply a URL writes the loopback / RFC1918 IPv4 target as e.g. `http://[2002:7f00:1::]/` (6to4 → 127.0.0.1), `http://[64:ff9b::7f00:1]/` (NAT64 → 127.0.0.1), `http://[::7f00:1]/` (IPv4-compatible → 127.0.0.1) or `http://[2001::1]/` (Teredo). `IpUtils::isPrivateIp()` returns `false` and `NoPrivateNetworkHttpClient` dispatches the request.

Real-world reachability of the embedded IPv4 depends on the deploy's IPv6 routing (6to4 tunnel interface, upstream NAT64 gateway, kernel handling of IPv4-compatible addresses), but the security boundary the decorator promises — the dispatch decision — is crossed regardless of whether the packet ultimately lands on the embedded IPv4.

### Resolution

The private-subnet list now includes `::/96`, `2002::/16`, `2001::/32`, `64:ff9b::/96` and `64:ff9b:1::/48`. Blanket blocking of these prefixes matches the policy applied by Chromium and Mozilla's Private Network Access; server-side HTTPS APIs are not legitimately published on these prefixes.

The patches for this issue are available [here](https://github.com/symfony/symfony/commit/82765368cf74177c36613575182f168a2eb765b2) for branch 5.4 and [here](https://github.com/symfony/symfony/commit/85b831555be8ea1f43bf01078afe87bc4c92f65e) for branch 6.4 (and forward-ported to 7.4, 8.0 and 8.1).

### Credits

Symfony would like to thank tonghuaroot for reporting the issue and Nicolas Grekas for providing the fix.

## Affected packages

- `symfony/http-client >= 5.4.0, < 5.4.53`
- `symfony/http-foundation >= 6.4.0, < 6.4.41`
- `symfony/http-foundation >= 7.0.0, < 7.4.13`
- `symfony/http-foundation >= 8.0.0, < 8.0.13`
- `symfony/symfony >= 5.4.0, < 5.4.53`
- `symfony/symfony >= 6.4.0, < 6.4.41`
- `symfony/symfony >= 7.0.0, < 7.4.13`
- `symfony/symfony >= 8.0.0, < 8.0.13`

## Remediation

Upgrade to a patched release:

- `symfony/http-client 5.4.53`
- `symfony/http-foundation 6.4.41`
- `symfony/http-foundation 7.4.13`
- `symfony/http-foundation 8.0.13`
- `symfony/symfony 5.4.53`
- `symfony/symfony 6.4.41`
- `symfony/symfony 7.4.13`
- `symfony/symfony 8.0.13`