CVE-2021-37859
Reflected XSS in OAuth Flow
Fixed a bypass for a reflected cross-site scripting vulnerability affecting OAuth-enabled instances of Mattermost.
Attack profile
How easy it is to exploit
- Attack vector
- Network
- Complexity
- High
- Privileges needed
- None
- User interaction
- Required
What an attacker can affect
- Confidentiality
- High
- Integrity
- High
- Availability
- Low
Exploit likelihood
What each source reports
CVE List Score used
Reflected XSS in OAuth Flow
Fixed a bypass for a reflected cross-site scripting vulnerability affecting OAuth-enabled instances of Mattermost.
- Record
CVE-2021-37859- CVSS 3.1
- 7.1 High
CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:L - Weakness
- CWE-79
- Updated
- 2026-11-02
EUVDEUVD-2021-24338
Fixed a bypass for a reflected cross-site scripting vulnerability affecting OAuth-enabled instances of Mattermost.
- Record
EUVD-2021-24338- CVSS 3.1
- 7.1 High
CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:L - Updated
- 2026-11-03
GitHub AdvisoriesGHSA-r4f6-w245-8wv4 No score
Fixed a bypass for a reflected cross-site scripting vulnerability affecting OAuth-enabled...
Fixed a bypass for a reflected cross-site scripting vulnerability affecting OAuth-enabled instances of Mattermost.
- Record
GHSA-r4f6-w245-8wv4- Weakness
- CWE-79
- Updated
- 2026-11-02
NVD
Fixed a bypass for a reflected cross-site scripting vulnerability affecting OAuth-enabled instances of Mattermost.
- Record
CVE-2021-37859- CVSS 3.1
- 7.1 High
CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:L - CVSS 3.1
- 6.1 Medium
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N - CVSS 2.0
- 4.3 Medium
AV:N/AC:M/Au:N/C:N/I:P/A:N - Weakness
- CWE-79
- Updated
- 2026-11-02
OSV
Fixed a bypass for a reflected cross-site scripting vulnerability affecting OAuth-enabled instances of Mattermost.
- Record
CVE-2021-37859- CVSS 3.1
- 6.1 Medium
CVSS:3.1/AV:N/AC:L/PR:N/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-2021-37859 is a high vulnerability (CVSS 7.1) in Mattermost, published August 5, 2021. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 3.29%, the 88th percentile. No source names a fixed version.