critical CVSS 9.8

CVE-2026-46634·PHP vulnerability

Twig is a template language for PHP. From 3.9.0 until 3.26.0, template_from_string() compiles an inner template under a synthesized __string_template__<hash> name that can fall outside a SourcePolicyInterface sandbox decision, allowing a sandboxed template that can call template_from_string and include to render an inner template without security policy enforcement. This issue is fixed in version 3.26.0.

Severity
critical
Software
PHP
Fixed in
3.26.0
Published
2026-07-14

Affected versions

From: 3.9.0

Until: 3.26.0

Fixed in: 3.26.0

How to fix this CVE

Update PHP and the Twig templating engine to version 3.26.0 or later to address a sandbox bypass vulnerability in the template_from_string() function. This vulnerability allows attackers to circumvent security policies when rendering dynamically generated templates. Immediately patch all production systems running affected versions to prevent unauthorized template execution.

sudo dnf update php php-twig

Defensia detects this vulnerability

How to check if you are affected

  1. Step 1: Check your installed PHP version with `php -v` and Twig version with `composer show symfony/twig-bundle` or `php -r "require 'vendor/autoload.php'; echo \Twig\Environment::VERSION;"` if using Composer
  2. Step 2: Identify if template_from_string() is used in your application by searching your codebase with `grep -r "template_from_string" --include="*.php" .`
  3. Step 3: Review access logs for patterns indicating template_from_string() calls with user-controlled input, particularly in request paths or POST parameters containing 'template' or 'string' keywords
  4. Step 4: After patching, verify the Twig version is 3.26.0+ with `php -r "require 'vendor/autoload.php'; echo \Twig\Environment::VERSION;"` and restart the web server with `sudo systemctl restart apache2` or `sudo systemctl restart nginx`

FAQ

What is CVE-2026-46634?

This is a sandbox bypass vulnerability in Twig's template_from_string() function that allows attackers to compile and execute templates outside the intended security policy enforcement. When a sandboxed template calls template_from_string() with dynamic content, the inner template bypasses security checks that would normally be applied.

Is CVE-2026-46634 being actively exploited?

No, this vulnerability is not currently listed in CISA's Known Exploited Vulnerabilities catalog and no public exploits are available. However, the critical CVSS score of 9.8 and low attack complexity make it a high-priority target for future exploitation.

What versions of PHP are affected by CVE-2026-46634?

Twig versions 3.9.0 through 3.25.x are affected. The fix is available in Twig 3.26.0 and later, which is typically bundled with PHP distributions via the php-twig package.

How do I check if my server is vulnerable to CVE-2026-46634?

Run `php -r "require 'vendor/autoload.php'; echo \Twig\Environment::VERSION;"` to check the Twig version. If it reports a version between 3.9.0 and 3.25.x, your system is vulnerable. Also check `composer.lock` for twig/twig versions in that range.

Does Defensia detect CVE-2026-46634?

Yes — Defensia's CVE advisory scanner compares installed package versions against the NVD database. If PHP with Twig is installed on a monitored server, CVE-2026-46634 will appear in your dashboard with remediation steps.

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References

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