CVE-2026-9820 | Mattermost schemes teams endpoint exposes private team invite IDs

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

Published: 2026-07-13 Last update: 2026-07-13 Assigner: [email protected] Source: [email protected]
NVD Status：Analyzed，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2026-9820 is rated Low Risk (16.9/100): CVSS Low severity, with low exploitation likelihood (EPSS 0.15%). Low composite risk—no urgent action required; patch on your normal maintenance cycle and revisit priority if CVSS or EPSS increases.

Risk is dynamic; we continuously reassess and refresh what is shown on this page as upstream context changes.

Exploit prediction scoring system (EPSS) score for CVE-2026-9820

EPSS lead: Daily EPSS estimates relative likelihood of exploitation; percentile ranks this CVE among scored vulnerabilities (higher = more severe relative rank).

# Date Old EPSS score New EPSS score Delta (New - Old)
1 2026-07-14 — 0.15% —

Full EPSS history (1 record total)

Common vulnerability scoring system (CVSS) metrics for CVE-2026-9820

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
3.8 3.1 LOW
CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/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:H)
They need powerful rights—admin, root, or similar—before this pays off.
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: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.
 1.2 2.5 [email protected]

Weakness enumeration for CVE-2026-9820

GitHub Security Advisory for CVE-2026-9820

GHSA-qvqh-cmq6-xvfq · Severity: low — Mattermost versions 11.7.x <= 11.7.2, 10.11.x <= 10.11.19 fail to sanitize team objects returned...

Affected software / configurations for CVE-2026-9820

Vendor Product Version Raw CPE
mattermost mattermost_server >= 10.11.0, < 10.11.20 cpe:2.3:a:mattermost:mattermost_server:*:*:*:*:*:*:*:*
mattermost mattermost_server >= 11.7.0, < 11.7.3 cpe:2.3:a:mattermost:mattermost_server:*:*:*:*:*:*:*:*

References for CVE-2026-9820

URL Tags
https://mattermost.com/security-updates Vendor Advisory
cvelogic Threat Intelligence