high CVSS 8.6

CVE-2026-48736·PHP vulnerability

Symfony is a PHP framework for web and console applications and a set of reusable PHP components. From 5.4.0 to 5.4.53, 6.4.41, 7.4.13, and 8.0.13, NoPrivateNetworkHttpClient and IpUtils::PRIVATE_SUBNETS omitted IPv6 transition prefixes such as 6to4, NAT64, Teredo, and IPv4-compatible IPv6, allowing attacker-supplied URLs to represent private IPv4 targets in forms that IpUtils::isPrivateIp() did not block. This issue is fixed in versions 5.4.53, 6.4.41, 7.4.13, and 8.0.13.

Severity
high
Software
PHP
Fixed in
8.0.13
Published
2026-07-14

Affected versions

From: 8.0.0

Until: 8.0.13

Fixed in: 8.0.13

How to fix this CVE

Update Symfony to version 8.0.13 or later to patch the IPv6 transition prefix bypass vulnerability in private network validation. This vulnerability allows attackers to craft URLs using IPv6 transition mechanisms (6to4, NAT64, Teredo, IPv4-compatible IPv6) to bypass private IP address restrictions and potentially access internal services. Immediately apply the security update and restart affected PHP applications.

sudo dnf update php

Defensia detects this vulnerability

How to check if you are affected

  1. Check installed PHP/Symfony version: php -v && composer show symfony/symfony 2>&1 | grep -i version
  2. Verify IpUtils and NoPrivateNetworkHttpClient components are in use: grep -r 'NoPrivateNetworkHttpClient\|IpUtils::isPrivateIp' /var/www --include='*.php' 2>/dev/null
  3. Search application logs for requests containing IPv6 transition prefixes: grep -iE '(2002:|64:ff9b::|::ffff:0:0|teredo|6to4)' /var/log/apache2/access.log /var/log/nginx/access.log 2>/dev/null
  4. Confirm patch applied: php -r 'echo phpversion(); echo "\n";' and verify no 8.0.0-8.0.12 versions remain in vendor/symfony/symfony/composer.json

FAQ

What is CVE-2026-48736?

This vulnerability affects Symfony's private network validation mechanisms, which fail to recognize IPv6 transition address formats (6to4, NAT64, Teredo, IPv4-compatible IPv6) as private addresses. Attackers can exploit this to bypass IP-based access controls designed to prevent requests to private or internal networks.

Is CVE-2026-48736 being actively exploited?

No, this vulnerability is not currently listed on the CISA Known Exploited Vulnerabilities (KEV) catalog and no public exploits are available. However, the attack pattern is straightforward enough that organizations should prioritize patching.

What versions of PHP are affected by CVE-2026-48736?

The vulnerability affects Symfony 5.4.0–5.4.52, 6.4.0–6.4.40, 7.4.0–7.4.12, and 8.0.0–8.0.12. Any PHP application using these Symfony versions is at risk, regardless of the PHP engine version itself.

How do I check if my server is vulnerable to CVE-2026-48736?

Run: composer show symfony/symfony 2>&1 | grep -i version. If the output shows versions in the affected ranges (e.g., 8.0.0 through 8.0.12), your installation is vulnerable. Also check: php -i | grep -i symfony

Does Defensia detect CVE-2026-48736?

Yes — Defensia's CVE advisory scanner compares installed package versions against the NVD database. If Symfony is installed on a monitored server, CVE-2026-48736 will appear in your dashboard with remediation steps.

Related PHP CVEs

CVE-2026-28289CVSS 10FreeScout is a free help desk and shared inbox built with PHP's Laravel framework. A patch bypass vulnerability for CVE-2026-27636 in FreeScout 1.8.206 and earlier allows any authenticated user with file upload permissions to achieve Remote Code Execution (RCE) on the server by uploading a malicious .htaccess file using a zero-width space character prefix to bypass the security check. The vulnerability exists in the sanitizeUploadedFileName() function in app/Http/Helper.php. The function contains a Time-of-Check to Time-of-Use (TOCTOU) flaw where the dot-prefix check occurs before sanitization removes invisible characters. This vulnerability is fixed in 1.8.207.
CVE-2025-46348CVSS 10YesWiki is a wiki system written in PHP. Prior to version 4.5.4, the request to commence a site backup can be performed and downloaded without authentication. The archives are created with a predictable filename, so a malicious user could create and download an archive without being authenticated. This could result in a malicious attacker making numerous requests to create archives and fill up the file system, or by downloading the archive which contains sensitive site information. This issue has been patched in version 4.5.4.
CVE-2025-47916CVSS 10Invision Community 5.0.0 before 5.0.7 allows remote code execution via crafted template strings to themeeditor.php. The issue lies within the themeeditor controller (file: /applications/core/modules/front/system/themeeditor.php), where a protected method named customCss can be invoked by unauthenticated users. This method passes the value of the content parameter to the Theme::makeProcessFunction() method; hence it is evaluated by the template engine. Accordingly, this can be exploited by unauthenticated attackers to inject and execute arbitrary PHP code by providing crafted template strings.
CVE-2025-25174CVSS 10Improper Control of Filename for Include/Require Statement in PHP Program ('PHP Remote File Inclusion') vulnerability in beeteam368 BeeTeam368 Extensions beeteam368-extensions allows PHP Local File Inclusion.This issue affects BeeTeam368 Extensions: from n/a through <= 1.9.4.
CVE-2025-62521CVSS 10ChurchCRM is an open-source church management system. Prior to version 5.21.0, a pre-authentication remote code execution vulnerability in ChurchCRM's setup wizard allows unauthenticated attackers to inject arbitrary PHP code during the initial installation process, leading to complete server compromise. The vulnerability exists in `setup/routes/setup.php` where user input from the setup form is directly concatenated into a PHP configuration template without any validation or sanitization. Any parameter in the setup form can be used to inject PHP code that gets written to `Include/Config.php`, which is then executed on every page load. This is more severe than typical authenticated RCE vulnerabilities because it requires no credentials and affects the installation process that administrators must complete. Version 5.21.0 patches the issue.

References

Track CVEs across your fleet automatically

Defensia scans your Linux servers and tells you exactly which ones are running vulnerable versions — including CVE-2026-48736. Free for 1 server.

Get started free