Bug 2571206 (CVE-2026-126074)

Summary: CVE-2026-126074 activestorage: activestorage: Denial of Service via filenames containing null bytes
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
Status: NEW --- QA Contact:
Severity: medium Docs Contact:
Priority: medium    
Version: unspecifiedCC: akostadi, amasferr, dmayorov, eshamard, jlledo, jvasik, kaycoth, pantinor, rblanco, tsedmik
Target Milestone: ---Keywords: Security
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Hardware: All   
OS: Linux   
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A flaw was found in Active Storage. A user permitted to upload file attachments can supply a filename containing a null byte, which is stored without proper sanitization. Subsequent application requests that attempt to view, preview, or process the uploaded attachment fail with an unhandled error, resulting in a persistent Denial of Service (DoS) on pages displaying the affected file.
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Description OSIDB Bzimport 2026-11-10 20:53:54 UTC 
Active Storage makes it simple to upload and reference files in cloud services and attach those files to Active Record objects. Prior to 8.1.4.1 and 8.0.5.2, ActiveStorage::Filename#base and #extension_with_delimiter, and therefore #extension, pass the stored filename unmodified to File.basename and File.extname, which raise ArgumentError when the name contains a NUL byte. Active Storage stores the client-supplied filename verbatim, so a user who is permitted to upload an attachment could persist such a filename on databases that accept NUL bytes in string columns, such as SQLite and MySQL/MariaDB. Each subsequent request that builds a variant or preview of the blob, opens it, or renders it as an Action Text attachment then raises, possibly resulting in a persistent DoS vulnerability for the pages that display the blob until it is purged or its filename is corrected. Applications that use PostgreSQL are not affected, because PostgreSQL rejects the row. This issue is fixed in versions 8.1.4.1 and 8.0.5.2.