Under certain circumstances, the Drupal core form API evaluates form element access incorrectly. This may lead to a user being able to alter data they should not have access to. No forms provided by Drupal core are known to be vulnerable. However, forms added through contributed or custom modules or themes may be affected.

Drupal core sanitizes filenames with dangerous extensions upon upload (reference: SA-CORE-2020-012) and strips leading and trailing dots from filenames to prevent uploading server configuration files (reference: SA-CORE-2019-010). However, the protections for these two vulnerabilities previously did not work correctly together. As a result, if the site were configured to allow the upload of files with an htaccess extension, these files' filenames would not be properly sanitized. This could allow bypassing the protections provided by Drupal core's default .htaccess files and possible remote code execution on Apache web servers. This issue is mitigated by the fact that it requires a field administrator to explicitly configure a file field to allow htaccess as an extension (a restricted permission), or a contributed module or custom code that overrides allowed file uploads.

In some situations, the Image module does not correctly check access to image files not stored in the standard public files directory when generating derivative images using the image styles system. Access to a non-public file is checked only if it is stored in the "private" file system. However, some contributed modules provide additional file systems, or schemes, which may lead to this vulnerability. This vulnerability is mitigated by the fact that it only applies when the site sets (Drupal 9) $config['image.settings']['allow_insecure_derivatives'] or (Drupal 7) $conf['image_allow_insecure_derivatives'] to TRUE. The recommended and default setting is FALSE, and Drupal core does not provide a way to change that in the admin UI. Some sites may require configuration changes following this security release. Review the release notes for your Drupal version if you have issues accessing files or image styles after updating.

Drupal core's form API has a vulnerability where certain contributed or custom modules' forms may be vulnerable to improper input validation. This could allow an attacker to inject disallowed values or overwrite data. Affected forms are uncommon, but in certain cases an attacker could alter critical or sensitive data.

Twig is a template language for PHP. Versions 1.x prior to 1.44.7, 2.x prior to 2.15.3, and 3.x prior to 3.4.3 encounter an issue when the filesystem loader loads templates for which the name is a user input. It is possible to use the `source` or `include` statement to read arbitrary files from outside the templates' directory when using a namespace like `@somewhere/../some.file`. In such a case, validation is bypassed. Versions 1.44.7, 2.15.3, and 3.4.3 contain a fix for validation of such template names. There are no known workarounds aside from upgrading.

guzzlehttp/psr7 is a PSR-7 HTTP message library. Versions prior to 1.8.4 and 2.1.1 are vulnerable to improper header parsing. An attacker could sneak in a new line character and pass untrusted values. The issue is patched in 1.8.4 and 2.1.1. There are currently no known workarounds.

CKEditor4 is an open source what-you-see-is-what-you-get HTML editor. CKEditor4 prior to version 4.18.0 contains a vulnerability in the `dialog` plugin. The vulnerability allows abuse of a dialog input validator regular expression, which can cause a significant performance drop resulting in a browser tab freeze. A patch is available in version 4.18.0. There are currently no known workarounds.

CKEditor4 is an open source what-you-see-is-what-you-get HTML editor. A vulnerability has been discovered in the core HTML processing module and may affect all plugins used by CKEditor 4 prior to version 4.18.0. The vulnerability allows someone to inject malformed HTML bypassing content sanitization, which could result in executing JavaScript code. This problem has been patched in version 4.18.0. There are currently no known workarounds.

Under some circumstances, the Drupal core JSON:API module does not properly restrict access to certain content, which may result in unintended access bypass. Sites that do not have the JSON:API module enabled are not affected.

Drupal's JSON:API and REST/File modules allow file uploads through their HTTP APIs. The modules do not correctly run all file validation, which causes an access bypass vulnerability. An attacker might be able to upload files that bypass the file validation process implemented by modules on the site.

Archive_Tar through 1.4.10 has :// filename sanitization only to address phar attacks, and thus any other stream-wrapper attack (such as file:// to overwrite files) can still succeed.

Archive_Tar through 1.4.10 allows an unserialization attack because phar: is blocked but PHAR: is not blocked.

In Symfony before 2.7.51, 2.8.x before 2.8.50, 3.x before 3.4.26, 4.x before 4.1.12, and 4.2.x before 4.2.7, a vulnerability would allow an attacker to authenticate as a privileged user on sites with user registration and remember me login functionality enabled. This is related to symfony/security.

In Symfony before 2.7.51, 2.8.x before 2.8.50, 3.x before 3.4.26, 4.x before 4.1.12, and 4.2.x before 4.2.7, when service ids allow user input, this could allow for SQL Injection and remote code execution. This is related to symfony/dependency-injection.

In Symfony before 2.7.51, 2.8.x before 2.8.50, 3.x before 3.4.26, 4.x before 4.1.12, and 4.2.x before 4.2.7, validation messages are not escaped, which can lead to XSS when user input is included. This is related to symfony/framework-bundle.

The PharStreamWrapper (aka phar-stream-wrapper) package 2.x before 2.1.1 and 3.x before 3.1.1 for TYPO3 does not prevent directory traversal, which allows attackers to bypass a deserialization protection mechanism, as demonstrated by a phar:///path/bad.phar/../good.phar URL.

jQuery before 3.4.0, as used in Drupal, Backdrop CMS, and other products, mishandles jQuery.extend(true, {}, ...) because of Object.prototype pollution. If an unsanitized source object contained an enumerable __proto__ property, it could extend the native Object.prototype.

In Drupal 7 versions prior to 7.65; Drupal 8.6 versions prior to 8.6.13;Drupal 8.5 versions prior to 8.5.14. Under certain circumstances the File module/subsystem allows a malicious user to upload a file that can trigger a cross-site scripting (XSS) vulnerability.

Some field types do not properly sanitize data from non-form sources in Drupal 8.5.x before 8.5.11 and Drupal 8.6.x before 8.6.10. This can lead to arbitrary PHP code execution in some cases. A site is only affected by this if one of the following conditions is met: The site has the Drupal 8 core RESTful Web Services (rest) module enabled and allows PATCH or POST requests, or the site has another web services module enabled, like JSON:API in Drupal 8, or Services or RESTful Web Services in Drupal 7. (Note: The Drupal 7 Services module itself does not require an update at this time, but you should apply other contributed updates associated with this advisory if Services is in use.)

In Drupal Core versions 7.x prior to 7.62, 8.6.x prior to 8.6.6 and 8.5.x prior to 8.5.9; A remote code execution vulnerability exists in PHP's built-in phar stream wrapper when performing file operations on an untrusted phar:// URI. Some Drupal code (core, contrib, and custom) may be performing file operations on insufficiently validated user input, thereby being exposed to this vulnerability. This vulnerability is mitigated by the fact that such code paths typically require access to an administrative permission or an atypical configuration.