CVE-2026-46639: Twig Sandbox Property And Method Bypass Vulnerability

HIGH
Advisory Identifier: GHSA-mm6w-gr99-p3jj
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CWE-693
Published
Advisory Summary

CVE-2026-46639 is a HIGH sandbox property and method bypass vulnerability (CWE-693: Protection Mechanism Failure) affecting Twig libraries in the Packagist ecosystem. The issue involves sandbox property and method bypass via object-destructuring assignment. Remediation is available by upgrading affected packages to version 3.26.0.

CVE-2026-46639 at a Glance

CVE Identifier CVE-2026-46639
GHSA Identifier GHSA-mm6w-gr99-p3jj
Severity HIGH
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-2026-46639

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-2026-46639, 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 object-destructuring assignment syntax introduced in Twig 3.24.0 generates a call to `CoreExtension::getAttribute()` with the `$sandboxed` argument hardcoded to `false`, regardless of whether a `SandboxExtension` is active. This permanently disables the sandbox's property and method policy checks for every destructuring expression. `ObjectDestructuringSetBinary::compile()` emits: ```php CoreExtension::getAttribute($this->env, $this->source, ..., \Twig\Template::ANY_CALL, false, false, false, ...); // ^^^^^ // sandbox check never runs ``` Whereas `GetAttrExpression::compile()` correctly passes `$env->hasExtension(SandboxExtension::class)`. An attacker with write access to a sandboxed Twig template can read any public property or invoke any public getter on objects passed to the template engine, bypassing `SecurityPolicy` restrictions. The exploit requires only the `{% do %}` tag to be in `allowedTags`, which is a common configuration. ### Resolution The destructuring compiler now forwards the active sandbox flag to `getAttribute()` so property/method allowlists are enforced. ### Credits Twig would like to thank Anvil Secure in collaboration with Claude and Anthropic Research for reporting and fixing the issue.

CVE-2026-46639 Affected Twig Versions

1 component(s)
Fixed Versions:
3.26.0
Product / Package Ecosystem Affected Versions Fixed Version
twig/twig
 Packagist
≥ 3.24.0
< 3.26.0
3.26.0

References

GitHub Advisory / Wiki ADVISORY
https://github.com/twigphp/Twig/security/advisories/GHSA-mm6w-gr99-p3jj
Twig Source Repository REPOSITORY
https://github.com/FriendsOfPHP/security-advisories/blob/master/twig/twig/CVE-2026-46639.yaml
Twig Source Repository REPOSITORY
https://github.com/twigphp/Twig
symfony.com/cve-2026-46639 WEB
https://symfony.com/cve-2026-46639

Frequently Asked Questions

What is CVE-2026-46639?
CVE-2026-46639 is a security vulnerability in Twig involving Sandbox property and method bypass via object-destructuring assignment 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-2026-46639?
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-2026-46639?
CVE-2026-46639 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-2026-46639?
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-mm6w-gr99-p3jj",
  "modified" : "2026-05-21T21:30:49Z",
  "published" : "2026-05-21T21:30:49Z",
  "aliases" : [ "CVE-2026-46639" ],
  "summary" : "Twig: Sandbox property and method bypass via object-destructuring assignment",
  "details" : "### Description\n\nThe object-destructuring assignment syntax introduced in Twig 3.24.0 generates a call to `CoreExtension::getAttribute()` with the `$sandboxed` argument hardcoded to `false`, regardless of whether a `SandboxExtension` is active. This permanently disables the sandbox's property and method policy checks for every destructuring expression.\n\n`ObjectDestructuringSetBinary::compile()` emits:\n\n```php\nCoreExtension::getAttribute($this->env, $this->source, ..., \\Twig\\Template::ANY_CALL, false, false, false, ...);\n//                                                                                ^^^^^\n//                                                                       sandbox check never runs\n```\n\nWhereas `GetAttrExpression::compile()` correctly passes `$env->hasExtension(SandboxExtension::class)`.\n\nAn attacker with write access to a sandboxed Twig template can read any public property or invoke any public getter on objects passed to the template engine, bypassing `SecurityPolicy` restrictions. The exploit requires only the `{% do %}` tag to be in `allowedTags`, which is a common configuration.\n\n### Resolution\n\nThe destructuring compiler now forwards the active sandbox flag to `getAttribute()` so property/method allowlists are enforced.\n\n### Credits\n\nTwig would like to thank Anvil Secure in collaboration with Claude and Anthropic Research for reporting and fixing the issue.",
  "severity" : [ {
    "type" : "CVSS_V4",
    "score" : "CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "Packagist",
      "name" : "twig/twig"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "3.24.0"
      }, {
        "fixed" : "3.26.0"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/twigphp/Twig/security/advisories/GHSA-mm6w-gr99-p3jj"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/FriendsOfPHP/security-advisories/blob/master/twig/twig/CVE-2026-46639.yaml"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/twigphp/Twig"
  }, {
    "type" : "WEB",
    "url" : "https://symfony.com/cve-2026-46639"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-693" ],
    "severity" : "HIGH",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-05-21T21:30:49Z",
    "nvd_published_at" : null
  }
}