NVD / CVE Program· CNA Mattermost

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

Noroxi assessment

Priority: Monitor (action score 15/100)

The sources we track (CISA KEV, Exploit-DB, Metasploit, Nuclei, GitHub) show no public exploit code or exploitation in the wild.
Probability of exploitation in the next 30 days: 0.25% (FIRST EPSS).
Anyone who can reach it over the internet can trigger it. Administrator privileges are required. No user action is required. No special conditions are required; it is repeatable.
According to the record, no fixed version is available yet.

Low priority for now. Update when a fix is released; follow the vendor's advisory.

Generated automatically from the record's data: CVSS (NVD and CNA), CISA KEV and SSVC, FIRST EPSS, exploit sources, fixed versions. How we calculate it

Primary sources: NVD · CVE.org · FIRST EPSS

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

LowCVSS 3.8 · v3.1—No exploit No fix recorded

Broken access control (IDOR)

Published: Jul 13, 2026
Updated: Jul 13, 2026
EPSS: 0.2% · 17th percentile
CWE: CWE-862

Report tools

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Action score

Monitor

Low priority for now.

CVSS: 15 / 40 · 3.8 / 10
CISA KEV: 0 / 30 · Not listed
EPSS: 0 / 30 · 0.2%

CISA SSVC decision

Exploitation: none
Automatable: no
Technical impact: partial

Vulnrichment: CISA's decision-tree inputs.

CNA vs NVD score

NVD: —
CNA · Mattermost: 3.8; NVD has not scored this yet; the score shown is the CNA’s.

The score given by the assigning authority versus NVD’s independent score. A gap means the severity is contested.

Get told when this record changes

Not in KEV: no record of exploitation in the wild
No public exploit code on record
No fixed version yet

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Noroxi analysis

What does it mean in your environment?

The assessment above is generated automatically from the record's data; it doesn't know your environment. Our team verifies on your systems whether this vulnerability is actually exploitable and which mitigation is enough.

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Affected systems

Is your version affected?

Pick the product and type the version you run. It's compared with this record's version ranges in your browser; the version isn't sent anywhere.

Vendor	Product	CPE
mattermost	mattermost server	cpe:2.3:a:mattermost:mattermost_server

Affected versions

NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.

mattermost mattermost server10.11.0 and later · before 10.11.20
mattermost mattermost server11.7.0 and later · before 11.7.3

Versions reported by the vendor

Affected version ranges reported by the assigning authority (Mattermost). Independent of NVD's CPE analysis and usually ahead of it.

Mattermost Mattermost
- 11.8.0, 11.7.3, 10.11.20not affected
- 11.7.0 and later · up to and including 11.7.2affected · semver
- 10.11.0 and later · up to and including 10.11.19affected · semver

Same product

mattermost: all records

Other highest-scoring records for the same primary product.

CVE-2026-4858Path traversal in integration action URL leading to arbitrary API execution via system admin’s auth token.
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CVE-2025-12421Account Takeover via Code Exchange Endpoint
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CVE-2025-12419Account takeover on OAuth/OpenID-enabled servers
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Published before and after this one in the same product

← EarlierCVE-2026-9708Jul 13, 2026 · Incoming webhook user attribution via unvalidated webhook owner
19Monitor
← EarlierCVE-2026-6541Jul 13, 2026 · Unscoped updates to other playbooks' metric configuration
17Monitor
Later →CVE-2026-9824Jul 13, 2026 · Remote cluster metadata enumeration via /share-channel autocomplete
17Monitor

Remediation

Which version to upgrade to

Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.

No fix version is recorded for this entry. Check the references for vendor advisories.

Exploit status

No known public exploit

No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.

Research context

For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.

Timeline

From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.

No dated events beyond publication.

EPSS, last 120 days

FIRST EPSS daily score; only changes of 0.01 or more are recorded (step chart).

Patch and commit links

Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.

No commit or PR link among the references.

Credits

All researchers

Finders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.

0x7oda7123finder

Variant candidates

Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.

CVE-2025-58073270 days apartArbitrary Mattermost Team can be joined by manipulating the OAuth state
32Monitor
CVE-2025-58075270 days apartArbitrary Mattermost Team can be joined by manipulating the SAML RelayState
32Monitor
CVE-2026-882163 days apartPlaybooks run owner channel membership permission bypass
28Monitor
CVE-2026-311756 days apartInstance and webhook GitLab plugin commands were able to be run by non-admin users
26Monitor
CVE-2026-516356 days apartMissing authorization check in AI message rewrite endpoint allows access to private thread content
26Monitor
CVE-2025-9076301 days apartMattermost Server exposes sensitive user credentials during shared channel membership synchronization
26Monitor

Chain candidates

An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.

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Bug bounty scope