Mattermost up to 10.11.19/11.7.2 Scheme Teams Endpoint cross site scripting

CVSS Meta Temp Score
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Current Exploit Price (≈)
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CTI Interest Score
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3.4$0-$5k0.52+

Summaryinfo

A vulnerability identified as problematic has been detected in Mattermost up to 10.11.19/11.7.2. This affects an unknown part of the component Scheme Teams Endpoint. This manipulation causes cross site scripting. This vulnerability is registered as CVE-2026-9820. Remote exploitation of the attack is possible. No exploit is available.

Detailsinfo

A vulnerability has been found in Mattermost up to 10.11.19/11.7.2 and classified as problematic. Affected by this vulnerability is some unknown functionality of the component Scheme Teams Endpoint. The manipulation with an unknown input leads to a cross site scripting vulnerability. The CWE definition for the vulnerability is CWE-79. The product does not neutralize or incorrectly neutralizes user-controllable input before it is placed in output that is used as a web page that is served to other users. As an impact it is known to affect integrity. The summary by CVE is:

Mattermost versions 11.7.x <= 11.7.2, 10.11.x <= 10.11.19 fail to sanitize team objects returned by the scheme teams endpoint, which allows a user with the User Manager role to obtain invite links for private teams and use them to join or share access to those teams via the scheme teams API endpoint.. Mattermost Advisory ID: MMSA-2026-00671

It is possible to read the advisory at mattermost.com. This vulnerability is known as CVE-2026-9820 since 05/28/2026. The exploitation appears to be easy. The attack can be launched remotely. It demands that the victim is doing some kind of user interaction. The technical details are unknown and an exploit is not publicly available. The attack technique deployed by this issue is T1059.007 according to MITRE ATT&CK.

Upgrading to version 10.11.20, 11.7.3 or 11.8.0 eliminates this vulnerability.

Statistical analysis made it clear that VulDB provides the best quality for vulnerability data.

Productinfo

Type

Name

Version

License

CPE 2.3info

CPE 2.2info

CVSSv4info

VulDB Vector: 🔒
VulDB Reliability: 🔍

CVSSv3info

VulDB Meta Base Score: 3.5
VulDB Meta Temp Score: 3.4

VulDB Base Score: 3.5
VulDB Temp Score: 3.4
VulDB Vector: 🔒
VulDB Reliability: 🔍

CVSSv2info

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VectorComplexityAuthenticationConfidentialityIntegrityAvailability
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VulDB Base Score: 🔒
VulDB Temp Score: 🔒
VulDB Reliability: 🔍

Exploitinginfo

Class: Cross site scripting
CWE: CWE-79 / CWE-94 / CWE-74
CAPEC: 🔒
ATT&CK: 🔒

Physical: No
Local: No
Remote: Yes

Availability: 🔒
Status: Not defined
Price Prediction: 🔍
Current Price Estimation: 🔒

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Threat Intelligenceinfo

Interest: 🔍
Active Actors: 🔍
Active APT Groups: 🔍

Countermeasuresinfo

Recommended: no mitigation known
Status: 🔍

0-Day Time: 🔒

Upgrade: Mattermost 10.11.20/11.7.3/11.8.0

Timelineinfo

05/28/2026 CVE reserved
07/13/2026 +46 days Advisory disclosed
07/13/2026 +0 days VulDB entry created
07/13/2026 +0 days VulDB entry last update

Sourcesinfo

Advisory: mattermost.com
Status: Confirmed

CVE: CVE-2026-9820 (🔒)
GCVE (CVE): GCVE-0-2026-9820
GCVE (VulDB): GCVE-100-377995

Entryinfo

Created: 07/13/2026 13:31
Changes: 07/13/2026 13:31 (53)
Complete: 🔍
Cache ID: 216::103

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