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CVE-2021-32727

End-to-end encryption device setup did not verify public key

5.7 MediumFix available

Nextcloud Android Client is the Android client for Nextcloud. Clients using the Nextcloud end-to-end encryption feature download the public and private key via an API endpoint. In versions prior to 3.16.1, the Nextcloud Android client skipped a step that involved the client checking if a private key belonged to a previously downloaded public certificate. If the Nextcloud instance served a malicious public key, the data would be encrypted for this key and thus could be accessible to a malicious actor. The vulnerability is patched in version 3.16.1. As a workaround, do not add additional end-to-end encrypted devices to a user account.

Attack profile

How easy it is to exploit

Attack vector
Network
Complexity
Low
Privileges needed
Low
User interaction
Required

What an attacker can affect

Confidentiality
High
Integrity
None
Availability
None

Exploit likelihood

0.73%Down 0.3 points since Jul 13, 2021
90%50%10%1%

What each source reports

CVE List Score used 5.7

End-to-end encryption device setup did not verify public key

Nextcloud Android Client is the Android client for Nextcloud. Clients using the Nextcloud end-to-end encryption feature download the public and private key via an API endpoint. In versions prior to 3.16.1, the Nextcloud Android client skipped a step that involved the client checking if a private key belonged to a previously downloaded public certificate. If the Nextcloud instance served a malicious public key, the data would be encrypted for this key and thus could be accessible to a malicious actor. The vulnerability is patched in version 3.16.1. As a workaround, do not add additional end-to-end encrypted devices to a user account.

Record
CVE-2021-32727
CVSS 3.1
5.7 MediumCVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:H/I:N/A:N
Weakness
CWE-295
Updated
2026-11-02
EUVDEUVD-2021-19509 5.7

Nextcloud Android Client is the Android client for Nextcloud. Clients using the Nextcloud end-to-end encryption feature download the public and private key via an API endpoint. In versions prior to 3.16.1, the Nextcloud Android client skipped a step that involved the client checking if a private key belonged to a previously downloaded public certificate. If the Nextcloud instance served a malicious public key, the data would be encrypted for this key and thus could be accessible to a malicious actor. The vulnerability is patched in version 3.16.1. As a workaround, do not add additional end-to-end encrypted devices to a user account.

Record
EUVD-2021-19509
CVSS 3.1
5.7 MediumCVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:H/I:N/A:N
Updated
2026-11-03
NVD 5.7

Nextcloud Android Client is the Android client for Nextcloud. Clients using the Nextcloud end-to-end encryption feature download the public and private key via an API endpoint. In versions prior to 3.16.1, the Nextcloud Android client skipped a step that involved the client checking if a private key belonged to a previously downloaded public certificate. If the Nextcloud instance served a malicious public key, the data would be encrypted for this key and thus could be accessible to a malicious actor. The vulnerability is patched in version 3.16.1. As a workaround, do not add additional end-to-end encrypted devices to a user account.

Record
CVE-2021-32727
CVSS 3.1
5.7 MediumCVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:H/I:N/A:N
CVSS 3.1
7.5 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
CVSS 2.0
5.0 MediumAV:N/AC:L/Au:N/C:P/I:N/A:N
Weakness
CWE-295
Updated
2026-11-02
OSV 7.5

Nextcloud Android Client is the Android client for Nextcloud. Clients using the Nextcloud end-to-end encryption feature download the public and private key via an API endpoint. In versions prior to 3.16.1, the Nextcloud Android client skipped a step that involved the client checking if a private key belonged to a previously downloaded public certificate. If the Nextcloud instance served a malicious public key, the data would be encrypted for this key and thus could be accessible to a malicious actor. The vulnerability is patched in version 3.16.1. As a workaround, do not add additional end-to-end encrypted devices to a user account.

Record
CVE-2021-32727
CVSS 3.1
7.5 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
Updated
2026-11-02
OSVBIT-nextcloud-2021-32727 No score

End-to-end encryption device setup did not verify public key

Nextcloud Android Client is the Android client for Nextcloud. Clients using the Nextcloud end-to-end encryption feature download the public and private key via an API endpoint. In versions prior to 3.16.1, the Nextcloud Android client skipped a step that involved the client checking if a private key belonged to a previously downloaded public certificate. If the Nextcloud instance served a malicious public key, the data would be encrypted for this key and thus could be accessible to a malicious actor. The vulnerability is patched in version 3.16.1. As a workaround, do not add additional end-to-end encrypted devices to a user account.

Record
BIT-nextcloud-2021-32727
Updated
2026-11-02

Affected products

Affected packages

Affected packages
PackageAffectedFixed
nextcloud
Bitnami
before 3.16.1
3.16.1

History

History
RecordedChangedSources
aliases, productsEUVD
first indexedCVE List, NVD, OSV

Dates are when Every CVE recorded each change. Upstream dates may differ.

In short

CVE-2021-32727 is a medium vulnerability (CVSS 5.7) in Nextcloud, published July 12, 2021. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 0.73%, the 54th percentile. Fixed in nextcloud 3.16.1.

References

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