CVE-2021-32726 [High] | Authentication Bypass in Nextcloud Server

Nextcloud Server is a Nextcloud package that handles data storage. In versions prior to 19.0.13, 20.011, and 21.0.3, webauthn tokens were not deleted after a user has been deleted. If a victim reused an earlier used username, the previous user could gain access to their account. The issue was fixed in versions 19.0.13, 20.0.11, and 21.0.3. There are no known workarounds.

#	Date	Old EPSS score	New EPSS score	Delta (New - Old)
1	2026-06-15	0.55%	1.78%	+1.23%
2	2025-11-21	0.63%	0.55%	-0.08%
3	2025-11-18	—	0.63%	—

Date

Old EPSS score

New EPSS score

Delta (New - Old)

2026-06-15

0.55%

1.78%

+1.23%

2025-11-21

0.63%

0.55%

-0.08%

2025-11-18

—

0.63%

—

Base score	Version	Severity	Vector	Exploitability	Impact	Score source
7.1	3.1	HIGH	`CVSS:3.1/AV:N/AC:H/PR:L/UI:R/S:U/C:H/I:H/A:H` Click to expand Attack vector (AV:N) Could be attacked over the internet or any normal routed network—not just someone sitting at the machine. Attack complexity (AC:H) Even with access, the exploit needs extra luck, timing, or a fussy environment to actually work. Privileges required (PR:L) A normal user session is enough; they don’t have to be admin. User interaction (UI:R) A real person has to do something—click, install, enable—otherwise it doesn’t land. Scope (S:U) Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems. Confidentiality (C:H) Serious risk that confidential data gets exposed in a big way. Integrity (I:H) They could widely tamper with or forge data—trust in the data is badly hurt. Availability (A:H) Could take the service down hard or make it unusable for people who depend on it.	1.2	5.9	[email protected]
9.8	3.1	CRITICAL	`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H` Click to expand Attack vector (AV:N) Could be attacked over the internet or any normal routed network—not just someone sitting at the machine. Attack complexity (AC:L) Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup. Privileges required (PR:N) No account or special rights needed—anonymous or random user is enough. User interaction (UI:N) Nobody has to click “OK” or open a trap file; it can work without a victim helping. Scope (S:U) Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems. Confidentiality (C:H) Serious risk that confidential data gets exposed in a big way. Integrity (I:H) They could widely tamper with or forge data—trust in the data is badly hurt. Availability (A:H) Could take the service down hard or make it unusable for people who depend on it.	3.9	5.9	[email protected]
7.5	2.0	HIGH	`AV:N/AC:L/Au:N/C:P/I:P/A:P` Click to expand Access vector (AV:N) Can be exploited remotely over network reachability. Access complexity (AC:L) Exploitation conditions are straightforward and predictable. Authentication (AU:N) No authentication is required. Confidentiality impact (C:P) Partial confidentiality impact. Integrity impact (I:P) Partial integrity impact. Availability impact (A:P) Partial availability impact.	10.0	6.4	[email protected]

Base score

Version

Severity

Vector

Exploitability

Impact

Score source

7.1

3.1

HIGH

CVSS:3.1/AV:N/AC:H/PR:L/UI:R/S:U/C:H/I:H/A:H Click to expand

Attack vector (AV:N): Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:H): Even with access, the exploit needs extra luck, timing, or a fussy environment to actually work.
Privileges required (PR:L): A normal user session is enough; they don’t have to be admin.
User interaction (UI:R): A real person has to do something—click, install, enable—otherwise it doesn’t land.
Scope (S:U): Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:H): Serious risk that confidential data gets exposed in a big way.
Integrity (I:H): They could widely tamper with or forge data—trust in the data is badly hurt.
Availability (A:H): Could take the service down hard or make it unusable for people who depend on it.

1.2

5.9

[email protected]

9.8

3.1

CRITICAL

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H Click to expand

Attack vector (AV:N): Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:L): Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:N): No account or special rights needed—anonymous or random user is enough.
User interaction (UI:N): Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U): Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:H): Serious risk that confidential data gets exposed in a big way.
Integrity (I:H): They could widely tamper with or forge data—trust in the data is badly hurt.
Availability (A:H): Could take the service down hard or make it unusable for people who depend on it.

3.9

5.9

[email protected]

7.5

2.0

HIGH

AV:N/AC:L/Au:N/C:P/I:P/A:P Click to expand

Access vector (AV:N): Can be exploited remotely over network reachability.
Access complexity (AC:L): Exploitation conditions are straightforward and predictable.
Authentication (AU:N): No authentication is required.
Confidentiality impact (C:P): Partial confidentiality impact.
Integrity impact (I:P): Partial integrity impact.
Availability impact (A:P): Partial availability impact.

10.0

6.4

[email protected]

OS Trackers for CVE-2021-32726

vendor	priority	summary	link
`gentoo`	low	CVE-2021-32726: 1 GLSA(s) (202208-17), 1 atom(s) (www-apps/nextcloud); latest impact low.	https://bugs.gentoo.org/buglist.cgi?quicksearch=CVE-2021-32726

Affected software / configurations for CVE-2021-32726

Vendor	Product	Version	Raw CPE
nextcloud	nextcloud_server	< 19.0.13	cpe:2.3:a:nextcloud:nextcloud_server::::::::
nextcloud	nextcloud_server	>= 20.0.0, < 20.0.11	cpe:2.3:a:nextcloud:nextcloud_server::::::::
nextcloud	nextcloud_server	>= 21.0.0, < 21.0.3	cpe:2.3:a:nextcloud:nextcloud_server::::::::

References for CVE-2021-32726

URL	Tags
https://github.com/nextcloud/security-advisories/security/advisories/GHSA-6qr9-c846-j8mg	Third Party Advisory
https://github.com/nextcloud/server/pull/27532	Third Party Advisory
https://hackerone.com/reports/1202590	Permissions Required
https://security.gentoo.org/glsa/202208-17	Third Party Advisory

URL

CVE-2021-32726 | Webauthn tokens not removed after user has been deleted

Exploit prediction scoring system (EPSS) score for CVE-2021-32726

Common vulnerability scoring system (CVSS) metrics for CVE-2021-32726

Weakness enumeration for CVE-2021-32726

OS Trackers for CVE-2021-32726

Affected software / configurations for CVE-2021-32726

References for CVE-2021-32726