CVE-2019-6340: Drupal Core Remote Code Execution Vulnerability

CVE-2019-6340 is a remote code execution vulnerability in Drupal Core. Certain field types fail to properly sanitize data that arrives from non-form sources, which can allow an attacker to achieve arbitrary PHP code execution on the server in some configurations. For teams running Drupal, this matters because successful exploitation can give an attacker the ability to run code in the context of the web application, potentially leading to full site compromise.

Public detail is limited to the high-level description above; exact affected releases, preconditions, and patch identifiers must be confirmed against the vendor advisory. CISA lists the required action as applying updates per vendor instructions. Ransomware use is not documented for this CVE.

How it works

The underlying weakness is CWE-502 (Deserialization of Untrusted Data). In Drupal Core, some field types do not adequately sanitize or validate data that is supplied outside normal form submission paths. When that data is later processed in a way that involves unserialization or equivalent handling of untrusted input, an attacker who can supply crafted content may cause the application to execute arbitrary PHP code.

At a technical level, the abuse path relies on the application accepting and processing attacker-controlled data through those field types without the same sanitization applied to ordinary form input. The result, in vulnerable setups, is code execution on the host running Drupal. Specific exploit mechanics, required privileges, or exact data formats are not provided in the available facts and should not be assumed; defenders should treat any untrusted input reaching those field-handling paths as potentially dangerous until the site is patched and verified.

Am I affected? How to find it in your systems

Drupal Core is commonly deployed as the foundation for public websites, intranets, and content-management platforms, often on LAMP/LEMP stacks or equivalent PHP hosting. Inventory every instance: check package managers, Composer lock files, Drupal’s own status report or admin UI version display, configuration-management inventories, and container or VM images that bundle Drupal.

• Identify all Drupal Core installations and record the exact version string from the running code or vendor packaging.
• Compare those versions and any enabled field-related modules or configurations against the vendor advisory for CVE-2019-6340; do not rely on version guesses.
• Review how content and field data enter the system (APIs, imports, web services, or other non-form channels) because the flaw involves insufficient sanitization of data from non-form sources.
• For exploitation signs, examine web server and application logs for anomalous requests that target field or entity endpoints, unexpected PHP errors or warnings around serialization/unserialization, sudden creation of new admin users, unexpected file writes under the Drupal root or files directory, and outbound connections or process execution that do not match normal site behavior. Correlate with any WAF or IDS alerts that reference this CVE or generic PHP code-execution patterns.

If version or configuration details are unclear, treat the instance as potentially affected until confirmed clean against the advisory.

How to remediate

Patch first. Apply the Drupal Core updates specified in the vendor advisory for CVE-2019-6340, following the vendor’s instructions exactly. After upgrading, verify the running version and re-test critical field and content workflows.

• Confirm the update has been applied on every instance, including staging, development, and any cloned or containerized copies.
• As hardening for this class of issue (unsafe handling of untrusted data that can lead to code execution), restrict which roles or services can supply field data via non-form channels, disable unused field types or input formats, and ensure PHP and Drupal are configured to minimize unnecessary deserialization or dynamic code paths.
• Keep the entire stack (PHP, web server, and contributed modules) current, and remove or isolate any unused Drupal sites that still expose the vulnerable core.

CISA’s required action is to apply updates per vendor instructions; that remains the primary remediation.

If you can't patch immediately

Until the vendor update can be installed, reduce exposure with compensating controls tailored to this weakness and product class.

• Segment Drupal hosts so they are not directly reachable from untrusted networks; place them behind reverse proxies or application gateways that can enforce strict request filtering.
• Apply virtual patching via a WAF or reverse-proxy rules that block or challenge requests containing suspicious serialized or field-related payloads; tune rules carefully to avoid breaking legitimate traffic and confirm effectiveness against the advisory’s description.
• Temporarily disable or restrict non-form data entry paths (APIs, bulk imports, or services that populate the affected field types) if the business can tolerate the loss of functionality.
• Tighten file-system permissions, disable unnecessary PHP functions that aid code execution, and ensure the Drupal process runs with least privilege.
• Increase monitoring: alert on anomalous request patterns to field/entity endpoints, unexpected PHP process activity, new or modified PHP files under the web root, and authentication anomalies. Retain logs for later forensic review.

These measures only lower risk; they do not replace the vendor patch.

If your data may have been exposed

Actively exploited remote-code-execution vulnerabilities in web applications can lead to full site takeover and subsequent data theft or further lateral movement. If you have reason to believe an instance was vulnerable and reachable, investigate for compromise, rotate credentials and secrets that the application could access, and follow your incident-response process. You can run a free exposure scan of your email addresses against known breach data to check whether associated accounts have appeared in prior breaches while you complete containment and recovery.