CVE-2026-46638: Twig `{% Sandbox %}{% Include %}` Vulnerability

MODERATE
Advisory Identifier: GHSA-7fxw-r6jv-74c8
Share
CWE-693
Published
Advisory Summary

CVE-2026-46638 is a MODERATE `{% sandbox %}{% include %}` vulnerability (CWE-693: Protection Mechanism Failure) affecting Twig libraries in the Packagist ecosystem. The issue involves `{% sandbox %}{% include %}` skips checksecurity() on cached templates (incomplete fix for cve-2024-45411). Remediation is available by upgrading affected packages to version 3.26.0.

CVE-2026-46638 at a Glance

CVE Identifier CVE-2026-46638
GHSA Identifier GHSA-7fxw-r6jv-74c8
Severity MODERATE
CVSS v3.1 Base Score N/A
CWE Classification CWE-693: Protection Mechanism Failure
Affected Product Twig
Package Ecosystem Packagist
Published Date
Last Updated

How to Fix CVE-2026-46638

To remediate this vulnerability, upgrade all affected Twig dependencies to a patched release. Both direct and transitive dependencies should be checked, as frameworks or security libraries may pull in vulnerable versions transitively.

twig/twig fixed: 3.26.0 
Upgrade twig/twig to 3.26.0
Verify Direct and Transitive Dependencies

Run the following command in your project directory to verify that all resolved dependencies use the patched release: 

inspect dependencies for twig/twig

How to Check if You Are Affected

To determine whether your application is affected by CVE-2026-46638, inspect your project dependencies for Twig:

inspect dependencies for twig/twig

Analyze the terminal output to locate any version of Twig in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 3.26.0), your application is affected.

Note: Verify declared build manifests and deployed runtime container environments.

Technical Details

Vulnerability Mechanism & Technical Analysis

This vulnerability is classified under CWE-693: Protection Mechanism Failure, where the product does not use or incorrectly uses a protection mechanism that provides sufficient defense against directed attacks against the product. In Twig, software state validation or input boundaries are circumvented during processing. Review the official source advisory statement below for specific affected components, classes, and reproduction details.

Source Advisory Statement

### Description The fix for CVE-2024-45411 / GHSA-6j75-5wfj-gh66 added an explicit `$loaded->unwrap()->checkSecurity()` call in `CoreExtension::include()` so that a template already cached in `Environment::$loadedTemplates` is re-checked when included with `sandboxed = true`. The deprecated but still functional `{% sandbox %}{% include ... %}{% endsandbox %}` tag path was not updated: it compiles to `enableSandbox(); yield from $this->load(...)->unwrap()->yield(...); disableSandbox();` with no `checkSecurity()` re-invocation. If the included template was loaded once outside the sandbox in the same `Environment` instance, its constructor (and therefore its compiled `checkSecurity()` call) already ran while `isSandboxed()` was `false`, so the tags/filters/functions allowlist enforced by `SecurityPolicy::checkSecurity()` is never applied. An attacker who can author the included template gains access to every filter, function and tag registered in the environment, regardless of the sandbox policy. ### Resolution The compiled output of `{% sandbox %}{% include %}` now calls `checkSecurity()` on the loaded template, matching the behaviour of `CoreExtension::include()` with `sandboxed = true`. ### Credits Twig would like to thank Claude Mythos Preview (via Project Glasswing) for reporting the issue and providing the fix.

CVE-2026-46638 Affected Twig Versions

1 component(s)
Fixed Versions:
3.26.0
Product / Package Ecosystem Affected Versions Fixed Version
twig/twig
 Packagist
< 3.26.0
3.26.0

References

GitHub Advisory / Wiki ADVISORY
https://github.com/twigphp/Twig/security/advisories/GHSA-7fxw-r6jv-74c8
Twig Source Repository REPOSITORY
https://github.com/FriendsOfPHP/security-advisories/blob/master/twig/twig/CVE-2026-46638.yaml
GitHub Advisory / Wiki ADVISORY
https://github.com/advisories/GHSA-6j75-5wfj-gh66
Twig Source Repository REPOSITORY
https://github.com/twigphp/Twig
symfony.com/cve-2026-46638 WEB
https://symfony.com/cve-2026-46638

Frequently Asked Questions

What is CVE-2026-46638?
CVE-2026-46638 is a security vulnerability in Twig involving `{% sandbox %}{% include %}` skips checkSecurity() on cached templates (incomplete fix for CVE-2024-45411) under CWE-693: Protection Mechanism Failure.
Which Twig versions are affected?
Affected versions include releases prior to 3.26.0 across affected packages: twig/twig.
What version fixes CVE-2026-46638?
Upgrading to 3.26.0 (or the latest patched release for your respective branch) resolves the vulnerability.
Is twig/twig affected?
Yes, twig/twig is affected in releases prior to 3.26.0. Upgrade your dependency to 3.26.0 or later.
What CWE is associated with CVE-2026-46638?
CVE-2026-46638 is classified under CWE-693: Protection Mechanism Failure (The product does not use or incorrectly uses a protection mechanism that provides sufficient defense against directed attacks against the product.).
How can I check Packagist dependencies for CVE-2026-46638?
Run the dependency tree command: 'inspect dependencies for twig/twig'. This command lists direct and transitive dependencies in your build configuration so you can verify if a vulnerable version is resolved.
Machine-readable OSV JSON OSV v1.5 Schema
Normalized schema output
View Raw JSON 
{
  "schema_version" : "1.4.0",
  "id" : "GHSA-7fxw-r6jv-74c8",
  "modified" : "2026-05-21T21:28:28Z",
  "published" : "2026-05-21T21:28:28Z",
  "aliases" : [ "CVE-2026-46638" ],
  "summary" : "Twig: `{% sandbox %}{% include %}` skips checkSecurity() on cached templates (incomplete fix for CVE-2024-45411)",
  "details" : "### Description\n\nThe fix for CVE-2024-45411 / GHSA-6j75-5wfj-gh66 added an explicit `$loaded->unwrap()->checkSecurity()` call in `CoreExtension::include()` so that a template already cached in `Environment::$loadedTemplates` is re-checked when included with `sandboxed = true`.\n\nThe deprecated but still functional `{% sandbox %}{% include ... %}{% endsandbox %}` tag path was not updated: it compiles to `enableSandbox(); yield from $this->load(...)->unwrap()->yield(...); disableSandbox();` with no `checkSecurity()` re-invocation. If the included template was loaded once outside the sandbox in the same `Environment` instance, its constructor (and therefore its compiled `checkSecurity()` call) already ran while `isSandboxed()` was `false`, so the tags/filters/functions allowlist enforced by `SecurityPolicy::checkSecurity()` is never applied.\n\nAn attacker who can author the included template gains access to every filter, function and tag registered in the environment, regardless of the sandbox policy.\n\n### Resolution\n\nThe compiled output of `{% sandbox %}{% include %}` now calls `checkSecurity()` on the loaded template, matching the behaviour of `CoreExtension::include()` with `sandboxed = true`.\n\n### Credits\n\nTwig would like to thank Claude Mythos Preview (via Project Glasswing) for reporting the issue and providing the fix.",
  "severity" : [ {
    "type" : "CVSS_V4",
    "score" : "CVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:N/VC:N/VI:N/VA:N/SC:H/SI:H/SA:H"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "Packagist",
      "name" : "twig/twig"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "3.26.0"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/twigphp/Twig/security/advisories/GHSA-7fxw-r6jv-74c8"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/FriendsOfPHP/security-advisories/blob/master/twig/twig/CVE-2026-46638.yaml"
  }, {
    "type" : "ADVISORY",
    "url" : "https://github.com/advisories/GHSA-6j75-5wfj-gh66"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/twigphp/Twig"
  }, {
    "type" : "WEB",
    "url" : "https://symfony.com/cve-2026-46638"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-693" ],
    "severity" : "MODERATE",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-05-21T21:28:28Z",
    "nvd_published_at" : null
  }
}