CVE-2020-13664Public exploitNetwork attack vector

Remote code execution via predictable test-site HMAC

Published May 5, 2021 · Updated Aug 4, 2024

Remote code execution in Drupal Core 8.8.0 through 8.8.7, 8.9.0, and 9.0.0 allows remote attackers to execute arbitrary PHP code. The drupal_valid_test_ua() check reads a .htkey directory as though it were a file, reducing its HMAC key on Windows to a guessable bootstrap.inc creation time because fileinode() returns zero. Exploitation requires creation of that directory, achieved in the demonstration by luring a logged-in administrator when Interface Translation is enabled, after which a hidden test site and malicious serialized database entry provide code execution with web-server privileges.

CVSS severity8.8
High
EPSS probability2.98%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Remote code execution in Drupal Core 8.8.0 through 8.8.7, 8.9.0, and 9.0.0 allows remote attackers to execute arbitrary PHP code. The drupal_valid_test_ua() check reads a .htkey directory as though it were a file, reducing its HMAC key on Windows to a guessable bootstrap.inc creation time because fileinode() returns zero. Exploitation requires creation of that directory, achieved in the demonstration by luring a logged-in administrator when Interface Translation is enabled, after which a hidden test site and malicious serialized database entry provide code execution with web-server privileges.

The record

CVE
CVE-2020-13664
Published
May 5, 2021
Updated
Aug 4, 2024
Vendor
Drupal
Product
Drupal Core
Classifications
CWE-77, T1189, T1190
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. May 5, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 4, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=8.8.x <8.8.8
  2. Affected versionversion=8.9.x <8.9.1
  3. Affected versionversion=9.0.1 <9.0.1

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Drupal · Drupal Coreversion=8.8.x <8.8.8; version=8.9.x <8.9.1; version=9.0.1 <9.0.1

Published CVSS scores

8.8IBMCVSS:3.0/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
8.8GitHub Advisory DatabaseCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-77Improper Neutralization of Special Elements used in a Command ('Command Injection')
T1189Drive-by Compromise
T1190Exploit Public-Facing Application

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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