CVE-2022-21706 [High] | Security Bypass in Zulip Server

Zulip is an open-source team collaboration tool with topic-based threading. Zulip Server version 2.0.0 and above are vulnerable to insufficient access control with multi-use invitations. A Zulip Server deployment which hosts multiple organizations is vulnerable to an attack where an invitation created in one organization (potentially as a role with elevated permissions) can be used to join any other organization. This bypasses any restrictions on required domains on users' email addresses, may be used to gain access to organizations which are only accessible by invitation, and may be used to gain access with elevated privileges. This issue has been patched in release 4.10. There are no known workarounds for this issue. ### Patches _Has the problem been patched? What versions should users upgrade to?_ ### Workarounds _Is there a way for users to fix or remediate the vulnerability without upgrading?_ ### References _Are there any links users can visit to find out more?_ ### For more information If you have any questions or comments about this advisory, you can discuss them on the [developer community Zulip server](https://zulip.com/developer-community/), or email the [Zulip security team](mailto:[email protected]).

#	Date	Old EPSS score	New EPSS score	Delta (New - Old)
1	2026-06-26	1.33%	1.37%	+0.03%
2	2026-06-15	0.14%	1.33%	+1.20%
3	2025-11-21	—	0.14%	—

Date

Old EPSS score

New EPSS score

Delta (New - Old)

2026-06-26

1.33%

1.37%

+0.03%

2026-06-15

0.14%

1.33%

+1.20%

2025-11-21

—

0.14%

—

Base score	Version	Severity	Vector	Exploitability	Impact	Score source
7.2	3.1	HIGH	`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:L/A:N` 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:C) Breaking this can reach past the original component and bite other resources—bigger blast radius. Confidentiality (C:L) Some sensitive info could get out, but not a total data dump. Integrity (I:L) Attackers could change some data, but it’s limited—not everything goes. Availability (A:N) Service keeps running; no real outage angle.	3.9	2.7	[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

7.2

3.1

HIGH

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:L/A:N 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:C): Breaking this can reach past the original component and bite other resources—bigger blast radius.
Confidentiality (C:L): Some sensitive info could get out, but not a total data dump.
Integrity (I:L): Attackers could change some data, but it’s limited—not everything goes.
Availability (A:N): Service keeps running; no real outage angle.

3.9

2.7

[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]

Affected software / configurations for CVE-2022-21706

Vendor	Product	Version	Raw CPE
zulip	zulip_server	>= 2.0.0, < 4.10.0	cpe:2.3:a:zulip:zulip_server::::::::

References for CVE-2022-21706

URL	Tags
https://blog.zulip.com/2022/02/25/zulip-cloud-invitation-vulnerability/	Vendor Advisory
https://blog.zulip.com/2022/02/25/zulip-server-4-10-security-release/#cve-2022-21706	Vendor Advisory
https://github.com/zulip/zulip/commit/88917019f03860609114082cdc0f31a561503f9e	Patch Third Party Advisory
https://github.com/zulip/zulip/security/advisories/GHSA-6xmj-2wcm-p2jc	Third Party Advisory

URL

CVE-2022-21706 | Multi-use invitations can grant access to other organizations in Zulip

Exploit prediction scoring system (EPSS) score for CVE-2022-21706

Common vulnerability scoring system (CVSS) metrics for CVE-2022-21706

Weakness enumeration for CVE-2022-21706

Affected software / configurations for CVE-2022-21706

References for CVE-2022-21706