Bug 1995584 (CVE-2021-32728)

Summary: CVE-2021-32728 nextcloud-client: End-to-end encryption device setup did not verify public key
Product: [Other] Security Response Reporter: Michael Kaplan <mkaplan>
Component: vulnerabilityAssignee: Red Hat Product Security <security-response-team>
Status: CLOSED UPSTREAM QA Contact:
Severity: medium Docs Contact:
Priority: medium    
Version: unspecifiedCC: claudiorodrigo, comzeradd, gwync, jan.public, mailinglists, michel, nb, nonamedotc, taaem
Target Milestone: ---Keywords: Security
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Hardware: All   
OS: Linux   
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Last Closed: 2021-08-19 15:34:53 UTC Type: ---
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Bug Depends On: 1995585, 1995586    
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Description Michael Kaplan 2021-08-19 13:09:11 UTC 
The Nextcloud Desktop Client is a tool to synchronize files from Nextcloud Server with a computer. Clients using the Nextcloud end-to-end encryption feature download the public and private key via an API endpoint. In versions prior to 3.3.0, the Nextcloud Desktop client fails to check if a private key belongs to previously downloaded public certificate. If the Nextcloud instance serves a malicious public key, the data would be encrypted for this key and thus could be accessible to a malicious actor. This issue is fixed in Nextcloud Desktop Client version 3.3.0. There are no known workarounds aside from upgrading.

References:

https://github.com/nextcloud/security-advisories/security/advisories/GHSA-f5fr-5gcv-6cc5
https://github.com/nextcloud/desktop/pull/3338
https://hackerone.com/reports/1189162
Comment 1 Michael Kaplan 2021-08-19 13:09:31 UTC 
Created nextcloud-client tracking bugs for this issue:

Affects: epel-all [bug 1995586]
Affects: fedora-all [bug 1995585]
Comment 2 Product Security DevOps Team 2021-08-19 15:34:53 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.