CVE-2021-35210: Contao/core bundle Cross Site Scripting Vulnerability
MODERATECVE-2021-35210 is a MODERATE (CVSS 6.1) cross site scripting vulnerability (CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')) affecting Contao/core bundle libraries in the Packagist ecosystem. The issue involves cross site scripting in the system log. Remediation is available by upgrading affected packages to version 4.9.16, 4.11.5.
CVE-2021-35210 at a Glance
Security Impact
CVSS: 6.1
The security impact metrics below are parsed directly from the CVSS v3.1 vector string (CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N).
How to Fix CVE-2021-35210
To remediate this vulnerability, upgrade all affected Contao/core bundle dependencies to a patched release. Both direct and transitive dependencies should be checked, as frameworks or security libraries may pull in vulnerable versions transitively.
Upgrade contao/core-bundle to 4.9.16Upgrade contao/core-bundle to 4.11.5Upgrade contao/contao to 4.9.16Upgrade contao/contao to 4.11.5Run the following command in your project directory to verify that all resolved dependencies use the patched release:
inspect dependencies for contao/core-bundleHow to Check if You Are Affected
To determine whether your application is affected by CVE-2021-35210, inspect your project dependencies for Contao/core bundle:
inspect dependencies for contao/core-bundleAnalyze the terminal output to locate any version of Contao/core bundle in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 4.9.16), 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-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting'), where the product does not neutralize or incorrectly neutralizes user-controllable input before it is placed in output that is used as a web page that is served to other users. In Contao/core bundle, 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
CVE-2021-35210 Affected Contao/core bundle Versions
4 component(s)| Product / Package | Ecosystem | Affected Versions | Fixed Version |
|---|---|---|---|
|
contao/core-bundle
|
Packagist |
≥ 4.5.0
< 4.9.16
|
4.9.16
|
|
contao/core-bundle
|
Packagist |
≥ 4.10.0
< 4.11.5
|
4.11.5
|
|
contao/contao
|
Packagist |
≥ 4.5.0
< 4.9.16
|
4.9.16
|
|
contao/contao
|
Packagist |
≥ 4.10.0
< 4.11.5
|
4.11.5
|
References
Frequently Asked Questions
What is CVE-2021-35210?
Which Contao/core bundle versions are affected?
What version fixes CVE-2021-35210?
Is contao/core-bundle affected?
Is contao/contao affected?
What is the CVSS score of CVE-2021-35210?
What CWE is associated with CVE-2021-35210?
How can I check Packagist dependencies for CVE-2021-35210?
Machine-readable OSV JSON
OSV v1.5 Schema
{
"schema_version" : "1.4.0",
"id" : "GHSA-h58v-c6rf-g9f7",
"modified" : "2025-04-17T12:45:28Z",
"published" : "2021-07-01T17:00:04Z",
"aliases" : [ "CVE-2021-35210" ],
"summary" : "Cross site scripting in the system log",
"details" : "### Impact\n\nIt is possible to inject code into the `tl_log` table that will be executed in the browser when the system log is called in the back end.\n\n### Patches\n\nUpdate to Contao 4.9.16 or 4.11.5.\n\n### Workarounds\n\nDisable the system log module in the back end for all users (especially admin users).\n\n### References\n\nhttps://contao.org/en/security-advisories/cross-site-scripting-in-the-system-log-2021\n\n### For more information\n\nIf you have any questions or comments about this advisory, open an issue in [contao/contao](https://github.com/contao/contao/issues/new/choose).",
"severity" : [ {
"type" : "CVSS_V3",
"score" : "CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N"
} ],
"affected" : [ {
"package" : {
"ecosystem" : "Packagist",
"name" : "contao/core-bundle"
},
"ranges" : [ {
"type" : "ECOSYSTEM",
"events" : [ {
"introduced" : "4.5.0"
}, {
"fixed" : "4.9.16"
} ]
} ]
}, {
"package" : {
"ecosystem" : "Packagist",
"name" : "contao/core-bundle"
},
"ranges" : [ {
"type" : "ECOSYSTEM",
"events" : [ {
"introduced" : "4.10.0"
}, {
"fixed" : "4.11.5"
} ]
} ]
}, {
"package" : {
"ecosystem" : "Packagist",
"name" : "contao/contao"
},
"ranges" : [ {
"type" : "ECOSYSTEM",
"events" : [ {
"introduced" : "4.5.0"
}, {
"fixed" : "4.9.16"
} ]
} ]
}, {
"package" : {
"ecosystem" : "Packagist",
"name" : "contao/contao"
},
"ranges" : [ {
"type" : "ECOSYSTEM",
"events" : [ {
"introduced" : "4.10.0"
}, {
"fixed" : "4.11.5"
} ]
} ]
} ],
"references" : [ {
"type" : "WEB",
"url" : "https://github.com/contao/contao/security/advisories/GHSA-h58v-c6rf-g9f7"
}, {
"type" : "ADVISORY",
"url" : "https://nvd.nist.gov/vuln/detail/CVE-2021-35210"
}, {
"type" : "WEB",
"url" : "https://contao.org/en/security-advisories/cross-site-scripting-in-the-system-log-2021.html"
}, {
"type" : "WEB",
"url" : "https://github.com/FriendsOfPHP/security-advisories/blob/master/contao/contao/CVE-2021-35210.yaml"
}, {
"type" : "WEB",
"url" : "https://github.com/FriendsOfPHP/security-advisories/blob/master/contao/core-bundle/CVE-2021-35210.yaml"
}, {
"type" : "PACKAGE",
"url" : "https://github.com/contao/contao"
} ],
"database_specific" : {
"cwe_ids" : [ "CWE-79" ],
"severity" : "MODERATE",
"github_reviewed" : true,
"github_reviewed_at" : "2021-06-23T20:24:28Z",
"nvd_published_at" : "2021-06-23T11:15:00Z"
}
}