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Low, CVSS 2.6amended

Contao crawler leaks auth credentials to external hosts

CVE-2026-55824GHSA-3mr9-p497-58f6

What to do

Vendor fix available. Upgrade each affected package to the fixed version on its release line (contao/contao 5.7.7, 5.3.47; contao/core-bundle 5.7.7, 5.3.47), redeploy, then verify what is actually installed.

This page has no inventory attached, so it cannot say whether you are affected. A vendor fix is not proof that your deployment is fixed.

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Affected packages

  • Packagist contao/contao

    Affected
    >= 4.13.0, < 5.3.47>= 5.4.0, < 5.7.7
    Fixed in
    5.3.47, 5.7.7

  • Packagist contao/core-bundle

    Affected
    >= 4.13.0, < 5.3.47>= 5.4.0, < 5.7.7
    Fixed in
    5.3.47, 5.7.7

Sources

Severity and exploitation
Exploitation
No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.
CVSS
2.6 · CVSS:3.1/AV:N/AC:H/PR:L/UI:R/S:U/C:L/I:N/A:N
EPSS
  • CVE-2026-55824: 0.24% estimated exploitation activity in the next 30 days; percentile 15.60 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.
Source description

As published by the source; long descriptions are shortened.

Summary Contao's crawler tries to prevent confidential HTTP client options from being sent to external domains by creating a scoped client: full options for root page origins, cleaned options for everything else. The cleaner removes Cookie and Authorization headers, but it removes the non-Symfony option names basicauth and bearerauth instead of Symfony HttpClient's real authbasic and authbearer options. When contao.crawl.defaulthttpclientoptions contains Basic or Bearer authentication for a protected staging/production site, those credentials remain in the "clean" client used for external links or configured additional URIs. An attacker who can get an external URL crawled, for example through a link on a crawled page while the broken-link checker is enabled, can receive the crawler credentials. Technical Detail Root Cause Symfony HttpClient authentication options are authbasic and authbearer; Contao's own manual documents authbasic for crawler Basic Authentication. Because the…

Dates and revisions
Published by the source
Last modified by the source
Source last checked
  1. Revision 2 · amended ·

    Amended from ghsa record GHSA-3mr9-p497-58f6

  2. Revision 1 · created ·

    Published from osv record GHSA-3mr9-p497-58f6

Agent brief

Preview the exact text before you copy it. Commands are read-only suggestions; review them before running anything.

# Patch Next advisory brief: CVE-2026-55824

Advisory: Contao crawler leaks auth credentials to external hosts
IDs: CVE-2026-55824, GHSA-3mr9-p497-58f6
Record: https://patchnext.com/advisories/cve-2026-55824 (revision 2, source checked 26 Oct 2026, 14:50 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Low (CVSS 2.6)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: contao/contao 5.7.7, 5.3.47; contao/core-bundle 5.7.7, 5.3.47. A vendor fix does not mean a deployment is fixed.

## Affected components
- Packagist contao/contao: affected >= 4.13.0, < 5.3.47; >= 5.4.0, < 5.7.7; fixed in 5.3.47, 5.7.7
- Packagist contao/core-bundle: affected >= 4.13.0, < 5.3.47; >= 5.4.0, < 5.7.7; fixed in 5.3.47, 5.7.7

## Suggested inspection (read-only)
- Packagist contao/contao: check the installed version with your package manager.
- Packagist contao/core-bundle: check the installed version with your package manager.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on contao/contao, contao/core-bundle.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://osv.dev/vulnerability/GHSA-3mr9-p497-58f6 (OSV record GHSA-3mr9-p497-58f6 lists affected ranges: Packagist contao/contao >=4.13.0 =5.4.0 =4.13.0 =5.4.0 <5.7.7 (fixed))
- Verified: https://github.com/advisories/GHSA-3mr9-p497-58f6 (GitHub-reviewed advisory GHSA-3mr9-p497-58f6 lists affected ranges: Packagist contao/contao >=4.13.0 =5.4.0 =4.13.0 =5.4.0 <5.7.7)

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