https://feed.craftedsignal.io/products/active-storage/Trending threats, MITRE ATT&CK coverage, and detection metadata. Fed continuously.Hugoenhello@craftedsignal.iohello@craftedsignal.ioThu, 25 Jan 2024 12:00:00 +0000https://feed.craftedsignal.io/briefs/2024-01-rails-active-storage-path-traversal/Thu, 25 Jan 2024 12:00:00 +0000hello@craftedsignal.iohttps://feed.craftedsignal.io/briefs/2024-01-rails-active-storage-path-traversal/A path traversal vulnerability (CVE-2026-33195) exists in Rails Active Storage's DiskService#path_for, potentially allowing attackers to read, write, or delete arbitrary files on the server by crafting blob keys with path traversal sequences, impacting applications that pass user input as blob keys.A path traversal vulnerability has been identified in the Active Storage component of Ruby on Rails. Specifically, the vulnerability resides within the DiskService#path_for method. This method lacks proper validation to ensure that the resolved filesystem path remains within the designated storage root directory. An attacker can exploit this by crafting a blob key containing path traversal sequences, such as "../", to navigate outside the intended storage area. This can lead to unauthorized access, potentially allowing the reading, writing, or deletion of arbitrary files on the server. This vulnerability particularly impacts applications where user-supplied input is used to construct blob keys. The affected versions are Active Storage versions before 7.2.3.1, versions 8.0.0.beta1 up to 8.0.4.1, and versions 8.1.0.beta1 up to 8.1.2.1. The CVE associated with this vulnerability is CVE-2026-33195.

Attack Chain

1. An attacker identifies an application using a vulnerable version of Rails Active Storage.
2. The attacker finds an endpoint where user-controlled input is used as a blob key for Active Storage.
3. The attacker crafts a malicious blob key containing path traversal sequences (e.g., "../../../etc/passwd").
4. The application uses the attacker-controlled blob key within the DiskService#path_for method.
5. Due to insufficient validation, DiskService#path_for resolves a file path outside the intended storage directory.
6. The application attempts to read, write, or delete a file based on the attacker-controlled path.
7. The attacker gains unauthorized access to sensitive files or modifies critical system configurations.
8. The attacker achieves arbitrary code execution or data exfiltration by leveraging the ability to write to arbitrary files.

Impact

Successful exploitation of this vulnerability allows attackers to read, write, or delete arbitrary files on the server. The number of affected applications is currently unknown, but any application using a vulnerable version of Rails Active Storage and processing user-supplied blob keys is at risk. This can result in complete compromise of the affected server, including data theft, system modification, and denial of service. The severity of the impact depends on the privileges of the Rails application and the sensitivity of the data stored on the server.

Recommendation

• Upgrade to the latest patched versions of Active Storage: versions >= 7.2.3.1, >= 8.0.4.1, or >= 8.1.2.1 to remediate CVE-2026-33195.
• Implement server-side validation to sanitize blob keys and prevent path traversal attempts before passing them to DiskService#path_for.
• Deploy the Sigma rule "Detect Rails Active Storage Path Traversal Attempt" to monitor for exploitation attempts.
• Review application code to ensure that user-provided input is not directly used as blob keys without proper sanitization.

]]>highadvisoryrailsactive storagepath traversalcve-2026-33195https://feed.craftedsignal.io/briefs/2024-01-rails-active-storage-delete/Wed, 10 Jan 2024 12:00:00 +0000hello@craftedsignal.iohttps://feed.craftedsignal.io/briefs/2024-01-rails-active-storage-delete/A vulnerability in Rails Active Storage allows attackers to delete arbitrary files in the storage directory by exploiting glob metacharacters in blob keys passed to `Dir.glob`.A critical vulnerability exists in Active Storage, a component of the Rails web application framework, affecting versions prior to 8.1.2.1, 8.0.4.1, and 7.2.3.1. The vulnerability, identified as CVE-2026-33202, stems from the DiskService#delete_prefixed method's improper handling of glob metacharacters within blob keys. Specifically, the method passes blob keys directly to Dir.glob without proper escaping. An attacker who can control the input of blob keys, either through direct manipulation or custom generation, can inject glob metacharacters (e.g., *, ?, []) into the key. This allows the attacker to delete unintended files residing within the storage directory, potentially leading to data loss or service disruption. Successful exploitation requires the application to be configured to use the DiskService and the attacker to have a mechanism to influence the blob key.

Attack Chain

1. The attacker identifies a Rails application utilizing Active Storage and the DiskService.
2. The attacker discovers or engineers a method to influence the generation or modification of blob keys. This might involve exploiting an existing application vulnerability (e.g., SQL injection) or manipulating application logic.
3. The attacker crafts a malicious blob key containing glob metacharacters (e.g., evil*key).
4. The application attempts to delete a file using the crafted blob key via DiskService#delete_prefixed.
5. DiskService#delete_prefixed passes the malicious blob key to Dir.glob without proper escaping.
6. Dir.glob interprets the glob metacharacters, causing it to match multiple files in the storage directory based on the attacker's crafted pattern. For example, evil*key could match evilfilekey, evilotherkey, etc.
7. Dir.glob deletes all matching files from the storage directory.
8. The attacker achieves arbitrary file deletion, potentially leading to data loss or service disruption.

Impact

Successful exploitation of this vulnerability allows an attacker to delete arbitrary files within the Active Storage's configured storage directory. This could lead to significant data loss, potentially disrupting application functionality and impacting users. The severity is heightened when sensitive information is stored within the affected directories. Given the wide adoption of Rails, a successful widespread attack could impact a large number of applications across various sectors. The CVSS v3.1 base score for this vulnerability is 9.1 (Critical).

Recommendation

• Upgrade to Active Storage versions 8.1.2.1, 8.0.4.1, or 7.2.3.1 or later to incorporate the patch for CVE-2026-33202.
• Implement input validation and sanitization on blob keys to prevent the injection of glob metacharacters.
• Monitor application logs for suspicious file deletion activity, particularly within the Active Storage storage directory, using the provided Sigma rule.
• Implement principle of least privilege on the storage directory to limit the impact of file deletion.

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