CVE-2026-107848: Contao Cross-site Request Forgery Vulnerability

LOW
Advisory Identifier: GHSA-9ff2-p842-45wq
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CVSS 3.5
CWE-352
Published
Advisory Summary

CVE-2026-107848 is a LOW (CVSS 3.5) cross-site request forgery vulnerability (CWE-352: Cross-Site Request Forgery (CSRF)) affecting Contao libraries in the Packagist ecosystem. The issue involves cross-site request forgery in custom backend actions. Remediation is available by upgrading affected packages to version 5.3.50, 5.7.12.

CVE-2026-107848 at a Glance

CVE Identifier CVE-2026-107848
GHSA Identifier GHSA-9ff2-p842-45wq
Severity LOW
CVSS v3.1 Base Score 3.5
CWE Classification CWE-352: Cross-Site Request Forgery (CSRF)
Affected Product Contao
Package Ecosystem Packagist
Published Date
Last Updated

Security Impact

CVSS: 3.5

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:R/S:U/C:N/I:L/A:N).

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

How to Fix CVE-2026-107848

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

contao/core-bundle fixed: 5.3.50 
Upgrade contao/core-bundle to 5.3.50
contao/core-bundle fixed: 5.7.12 
Upgrade contao/core-bundle to 5.7.12
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 contao/core-bundle

How to Check if You Are Affected

To determine whether your application is affected by CVE-2026-107848, inspect your project dependencies for Contao:

inspect dependencies for contao/core-bundle

Analyze the terminal output to locate any version of Contao in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 5.3.50), 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-352: Cross-Site Request Forgery (CSRF), where the web application does not, or cannot, sufficiently verify whether a request was intentionally provided by the user who sent the request, which could have originated from an unauthorized actor. In Contao, 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

`RequestTokenListener` is the only generic `REQUEST_TOKEN` validator in Contao and it only runs on POST. On the GET side the guard is local and declarative, and it only fires when an `act` parameter is present. Every back end action dispatched through a different parameter therefore has no CSRF protection at all. This is a family rather than a single bug. ### Impact An attacker who gets a logged in back end user to load a URL performs back end actions as that user, with no token and no confirmation. Because the exposure follows from the dispatch mechanism rather than from one callback, every present and future `key=` action inherits it. **Honest bound.** The victim must be authenticated in the back end and must load the URL, and the reachable actions are limited to the modules that user can access. We have not found a `key=` action that grants privileges; the ones we verified are destructive or state changing rather than escalating.

CVE-2026-107848 Affected Contao Versions

2 component(s)
Fixed Versions:
5.3.505.7.12
Product / Package Ecosystem Affected Versions Fixed Version
contao/core-bundle
 Packagist
≥ 4.0.0
< 5.3.50
5.3.50
contao/core-bundle
 Packagist
≥ 5.4.0-RC1
< 5.7.12
5.7.12

References

GitHub Advisory / Wiki ADVISORY
https://github.com/contao/contao/security/advisories/GHSA-9ff2-p842-45wq
Security Fix Commit FIX COMMIT
https://github.com/contao/contao/commit/34dd27ee6739f10568d3d95d8784862255c925b4
Contao Source Repository REPOSITORY
https://github.com/contao/contao
Contao Release RELEASE
https://github.com/contao/contao/releases/tag/5.7.12

Frequently Asked Questions

What is CVE-2026-107848?
CVE-2026-107848 is a security vulnerability in Contao involving Cross-site request forgery in custom backend actions under CWE-352: Cross-Site Request Forgery (CSRF).
Which Contao versions are affected?
Affected versions include releases prior to 5.3.50, 5.7.12 across affected packages: contao/core-bundle.
What version fixes CVE-2026-107848?
Upgrading to 5.3.50, 5.7.12 (or the latest patched release for your respective branch) resolves the vulnerability.
Is contao/core-bundle affected?
Yes, contao/core-bundle is affected in releases prior to 5.3.50, 5.7.12. Upgrade your dependency to 5.3.50, 5.7.12 or later.
What is the CVSS score of CVE-2026-107848?
CVE-2026-107848 has a CVSS v3.1 base score of 3.5 (LOW) with vector string CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:N/I:L/A:N.
What CWE is associated with CVE-2026-107848?
CVE-2026-107848 is classified under CWE-352: Cross-Site Request Forgery (CSRF) (The web application does not, or cannot, sufficiently verify whether a request was intentionally provided by the user who sent the request, which could have originated from an unauthorized actor.).
How can I check Packagist dependencies for CVE-2026-107848?
Run the dependency tree command: 'inspect dependencies for contao/core-bundle'. 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-9ff2-p842-45wq",
  "modified" : "2026-10-09T20:54:00Z",
  "published" : "2026-10-09T20:54:00Z",
  "aliases" : [ "CVE-2026-107848" ],
  "summary" : "Contao: Cross-site request forgery in custom backend actions",
  "details" : "`RequestTokenListener` is the only generic `REQUEST_TOKEN` validator in Contao and it only runs on POST. On the GET side the guard is local and declarative, and it only fires when an `act` parameter is present. Every back end action dispatched through a different parameter therefore has no CSRF protection at all. This is a family rather than a single bug.\n\n### Impact\n\nAn attacker who gets a logged in back end user to load a URL performs back end actions as that user, with no token and no confirmation. Because the exposure follows from the dispatch mechanism rather than from one callback, every present and future `key=` action inherits it.\n\n**Honest bound.** The victim must be authenticated in the back end and must load the URL, and the reachable actions are limited to the modules that user can access. We have not found a `key=` action that grants privileges; the ones we verified are destructive or state changing rather than escalating.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:N/I:L/A:N"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "Packagist",
      "name" : "contao/core-bundle"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "4.0.0"
      }, {
        "fixed" : "5.3.50"
      } ]
    } ]
  }, {
    "package" : {
      "ecosystem" : "Packagist",
      "name" : "contao/core-bundle"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "5.4.0-RC1"
      }, {
        "fixed" : "5.7.12"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/contao/contao/security/advisories/GHSA-9ff2-p842-45wq"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/contao/contao/commit/34dd27ee6739f10568d3d95d8784862255c925b4"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/contao/contao"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/contao/contao/releases/tag/5.7.12"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-352" ],
    "severity" : "LOW",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-10-09T20:54:00Z",
    "nvd_published_at" : null
  }
}