CVE-2021-21408: Smarty/smarty Access To Restricted PHP Code Vulnerability

HIGH
Advisory Identifier: GHSA-4h9c-v5vg-5m6m
Share
CVSS 8.8
CWE-20
Published
Advisory Summary

CVE-2021-21408 is a HIGH (CVSS 8.8) access to restricted php code vulnerability (CWE-20: Improper Input Validation) affecting Smarty/smarty libraries in the Packagist ecosystem. The issue involves access to restricted php code by dynamic static class access in smarty. Remediation is available by upgrading affected packages to version 3.1.43, 4.0.3.

CVE-2021-21408 at a Glance

CVE Identifier CVE-2021-21408
GHSA Identifier GHSA-4h9c-v5vg-5m6m
Severity HIGH
CVSS v3.1 Base Score 8.8
CWE Classification CWE-20: Improper Input Validation
Affected Product Smarty/smarty
Package Ecosystem Packagist
Published Date
Last Updated

Security Impact

CVSS: 8.8

The security impact metrics below are parsed directly from the CVSS v3.1 vector string (CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H).

Attack Vector Network (AV:N)
Attack Complexity Low (AC:L)
Privileges Required Low (PR:L)
User Interaction None (UI:N)
Scope Unchanged (S:U)
Confidentiality High (C:H)
Integrity High (I:H)
Availability High (A:H)

How to Fix CVE-2021-21408

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

smarty/smarty fixed: 3.1.43 
Upgrade smarty/smarty to 3.1.43
smarty/smarty fixed: 4.0.3 
Upgrade smarty/smarty to 4.0.3
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 smarty/smarty

How to Check if You Are Affected

To determine whether your application is affected by CVE-2021-21408, inspect your project dependencies for Smarty/smarty:

inspect dependencies for smarty/smarty

Analyze the terminal output to locate any version of Smarty/smarty in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 3.1.43), 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-20: Improper Input Validation, where the product receives input or data, but it does not validate or incorrectly validates that the input has the properties that are required to process the data safely and correctly. In Smarty/smarty, 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

### Impact Template authors could run restricted static php methods. ### Patches Please upgrade to 3.1.40 or higher. ### References See the [documentation on Smarty security features](https://www.smarty.net/docs/en/advanced.features.tpl#advanced.features.security) on the static_classes access filter. ### For more information If you have any questions or comments about this advisory please open an issue in [the Smarty repo](https://github.com/smarty-php/smarty)

CVE-2021-21408 Affected Smarty/smarty Versions

2 component(s)
Fixed Versions:
3.1.434.0.3
Product / Package Ecosystem Affected Versions Fixed Version
smarty/smarty
 Packagist
< 3.1.43
3.1.43
smarty/smarty
 Packagist
≥ 4.0.0
< 4.0.3
4.0.3

References

GitHub Advisory / Wiki ADVISORY
https://github.com/smarty-php/smarty/security/advisories/GHSA-4h9c-v5vg-5m6m
NVD — CVE-2021-21408 NVD
https://nvd.nist.gov/vuln/detail/CVE-2021-21408
Security Fix Commit FIX COMMIT
https://github.com/smarty-php/smarty/commit/19ae410bf56007a5ef24441cdc6414619cfaf664
Smarty/smarty Source Repository REPOSITORY
https://github.com/FriendsOfPHP/security-advisories/blob/master/smarty/smarty/CVE-2021-21408.yaml
Smarty/smarty Source Repository REPOSITORY
https://github.com/smarty-php/smarty
Smarty/smarty Release RELEASE
https://github.com/smarty-php/smarty/releases/tag/v3.1.43
Smarty/smarty Release RELEASE
https://github.com/smarty-php/smarty/releases/tag/v4.0.3
lists.debian.org/debian-lts-announce... WEB
https://lists.debian.org/debian-lts-announce/2022/05/msg00005.html
lists.fedoraproject.org/archives/list/packa... WEB
https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/BRAJVDRGCIY5UZ2PQHKDTT7RMKG6WJQQ
lists.fedoraproject.org/archives/list/packa... WEB
https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/L777JIBIWJV34HS7LXPIDWASG7TT4LNI
Smarty/smarty Security Information SECURITY
https://security.gentoo.org/glsa/202209-09
Smarty/smarty Security Information SECURITY
https://www.debian.org/security/2022/dsa-5151

Frequently Asked Questions

What is CVE-2021-21408?
CVE-2021-21408 is a security vulnerability in Smarty/smarty involving Access to restricted PHP code by dynamic static class access in smarty under CWE-20: Improper Input Validation.
Which Smarty/smarty versions are affected?
Affected versions include releases prior to 3.1.43, 4.0.3 across affected packages: smarty/smarty.
What version fixes CVE-2021-21408?
Upgrading to 3.1.43, 4.0.3 (or the latest patched release for your respective branch) resolves the vulnerability.
Is smarty/smarty affected?
Yes, smarty/smarty is affected in releases prior to 3.1.43, 4.0.3. Upgrade your dependency to 3.1.43, 4.0.3 or later.
What is the CVSS score of CVE-2021-21408?
CVE-2021-21408 has a CVSS v3.1 base score of 8.8 (HIGH) with vector string CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H.
What CWE is associated with CVE-2021-21408?
CVE-2021-21408 is classified under CWE-20: Improper Input Validation (The product receives input or data, but it does not validate or incorrectly validates that the input has the properties that are required to process the data safely and correctly.).
How can I check Packagist dependencies for CVE-2021-21408?
Run the dependency tree command: 'inspect dependencies for smarty/smarty'. 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-4h9c-v5vg-5m6m",
  "modified" : "2022-01-20T15:33:55Z",
  "published" : "2022-01-12T22:43:42Z",
  "aliases" : [ "CVE-2021-21408" ],
  "summary" : "Access to restricted PHP code by dynamic static class access in smarty",
  "details" : "### Impact\nTemplate authors could run restricted static php methods.\n\n### Patches\nPlease upgrade to 3.1.40 or higher.\n\n### References\nSee the [documentation on Smarty security features](https://www.smarty.net/docs/en/advanced.features.tpl#advanced.features.security) on the static_classes access filter.\n\n### For more information\nIf you have any questions or comments about this advisory please open an issue in [the Smarty repo](https://github.com/smarty-php/smarty)\n",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "Packagist",
      "name" : "smarty/smarty"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "3.1.43"
      } ]
    } ]
  }, {
    "package" : {
      "ecosystem" : "Packagist",
      "name" : "smarty/smarty"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "4.0.0"
      }, {
        "fixed" : "4.0.3"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/smarty-php/smarty/security/advisories/GHSA-4h9c-v5vg-5m6m"
  }, {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2021-21408"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/smarty-php/smarty/commit/19ae410bf56007a5ef24441cdc6414619cfaf664"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/FriendsOfPHP/security-advisories/blob/master/smarty/smarty/CVE-2021-21408.yaml"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/smarty-php/smarty"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/smarty-php/smarty/releases/tag/v3.1.43"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/smarty-php/smarty/releases/tag/v4.0.3"
  }, {
    "type" : "WEB",
    "url" : "https://lists.debian.org/debian-lts-announce/2022/05/msg00005.html"
  }, {
    "type" : "WEB",
    "url" : "https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/BRAJVDRGCIY5UZ2PQHKDTT7RMKG6WJQQ"
  }, {
    "type" : "WEB",
    "url" : "https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/L777JIBIWJV34HS7LXPIDWASG7TT4LNI"
  }, {
    "type" : "WEB",
    "url" : "https://security.gentoo.org/glsa/202209-09"
  }, {
    "type" : "WEB",
    "url" : "https://www.debian.org/security/2022/dsa-5151"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-20" ],
    "severity" : "HIGH",
    "github_reviewed" : true,
    "github_reviewed_at" : "2022-01-10T22:09:37Z",
    "nvd_published_at" : "2022-01-10T20:15:00Z"
  }
}