CVE-2021-3866
Cross-site Scripting (XSS) - Stored in zulip/zulip
Cross-site Scripting (XSS) - Stored in GitHub repository zulip/zulip more than and including 44f935695d452cc3fb16845a0c6af710438b153d and prior to 3eb2791c3e9695f7d37ffe84e0c2184fae665cb6.
Attack profile
How easy it is to exploit
- Attack vector
- Network
- Complexity
- High
- Privileges needed
- High
- User interaction
- Required
What an attacker can affect
- Confidentiality
- High
- Integrity
- Low
- Availability
- Low
Exploit likelihood
What each source reports
CVE List Score used
Cross-site Scripting (XSS) - Stored in zulip/zulip
Cross-site Scripting (XSS) - Stored in GitHub repository zulip/zulip more than and including 44f935695d452cc3fb16845a0c6af710438b153d and prior to 3eb2791c3e9695f7d37ffe84e0c2184fae665cb6.
- Record
CVE-2021-3866- CVSS 3.0
- 6.8 Medium
CVSS:3.0/AV:N/AC:H/PR:H/UI:R/S:C/C:H/I:L/A:L - Weakness
- CWE-79
- Updated
- 2026-11-02
EUVDEUVD-2021-27101
Cross-site Scripting (XSS) - Stored in GitHub repository zulip/zulip more than and including 44f935695d452cc3fb16845a0c6af710438b153d and prior to 3eb2791c3e9695f7d37ffe84e0c2184fae665cb6.
- Record
EUVD-2021-27101- CVSS 3.0
- 6.8 Medium
CVSS:3.0/AV:N/AC:H/PR:H/UI:R/S:C/C:H/I:L/A:L - Updated
- 2026-11-03
GitHub AdvisoriesGHSA-c9g2-65fq-w8q5 No score
Cross-site Scripting (XSS) - Stored in GitHub repository zulip/zulip prior to main.
Cross-site Scripting (XSS) - Stored in GitHub repository zulip/zulip prior to main.
- Record
GHSA-c9g2-65fq-w8q5- Weakness
- CWE-79
- Updated
- 2026-11-02
NVD
Cross-site Scripting (XSS) - Stored in GitHub repository zulip/zulip more than and including 44f935695d452cc3fb16845a0c6af710438b153d and prior to 3eb2791c3e9695f7d37ffe84e0c2184fae665cb6.
- Record
CVE-2021-3866- CVSS 3.1
- 5.4 Medium
CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N - CVSS 3.0
- 6.8 Medium
CVSS:3.0/AV:N/AC:H/PR:H/UI:R/S:C/C:H/I:L/A:L - CVSS 2.0
- 3.5 Low
AV:N/AC:M/Au:S/C:N/I:P/A:N - Weakness
- CWE-79
- Updated
- 2026-11-02
OSV
Cross-site Scripting (XSS) - Stored in GitHub repository zulip/zulip more than and including 44f935695d452cc3fb16845a0c6af710438b153d and prior to 3eb2791c3e9695f7d37ffe84e0c2184fae665cb6.
- Record
CVE-2021-3866- CVSS 3.1
- 5.4 Medium
CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N - Updated
- 2026-11-02
Affected products
History
| Recorded | Changed | Sources |
|---|---|---|
| aliases | EUVD | |
| first indexed | CVE List, GitHub Advisories, NVD, OSV |
Dates are when Every CVE recorded each change. Upstream dates may differ.
In short
CVE-2021-3866 is a medium vulnerability (CVSS 6.8) in Zulip, published January 20, 2022. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 0.89%, the 59th percentile. No source names a fixed version.