Bug 1981818 (CVE-2021-32679)

Summary: CVE-2021-32679 nextcloud: filenames not escaped by default in controllers using DownloadResponse
Product: [Other] Security Response Reporter: Guilherme de Almeida Suckevicz <gsuckevi>
Component: vulnerabilityAssignee: Red Hat Product Security <security-response-team>
Status: CLOSED UPSTREAM QA Contact:
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Priority: low    
Version: unspecifiedCC: ce, james.hogarth
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Hardware: All   
OS: Linux   
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Last Closed: 2021-07-13 21:55:06 UTC Type: ---
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Bug Depends On: 1981819    
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Description Guilherme de Almeida Suckevicz 2021-07-13 13:40:01 UTC 
Nextcloud Server is a Nextcloud package that handles data storage. In versions prior to 19.0.13, 20.0.11, and 21.0.3, filenames where not escaped by default in controllers using `DownloadResponse`. When a user-supplied filename was passed unsanitized into a `DownloadResponse`, this could be used to trick users into downloading malicious files with a benign file extension. This would show in UI behaviours where Nextcloud applications would display a benign file extension (e.g. JPEG), but the file will actually be downloaded with an executable file extension. The vulnerability is patched in versions 19.0.13, 20.0.11, and 21.0.3. Administrators of Nextcloud instances do not have a workaround available, but developers of Nextcloud apps may manually escape the file name before passing it into `DownloadResponse`.

Reference:
https://github.com/nextcloud/security-advisories/security/advisories/GHSA-3hjp-26x8-mhf6
Comment 1 Guilherme de Almeida Suckevicz 2021-07-13 13:40:34 UTC 
Created nextcloud tracking bugs for this issue:

Affects: fedora-all [bug 1981819]
Comment 2 Product Security DevOps Team 2021-07-13 21:55:06 UTC 
This CVE Bugzilla entry is for community support informational purposes only as it does not affect a package in a commercially supported Red Hat product. Refer to the dependent bugs for status of those individual community products.