NVD / CVE Program· CNA Mattermost

CVE-2025-12559: Information Disclosure in Common Teams API

MediumCVSS 4.3 · v3.1—No exploit Fix available

Noroxi assessment

Priority: Monitor (action score 17/100)

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: 0.23% (FIRST EPSS).
Anyone who can reach it over the internet can trigger it. A low-privileged account is enough. No user action is required. No special conditions are required; it is repeatable.
Fixed version: github.com/mattermost/mattermost-server (Go) 10.11.5, 10.12.2, 10.5.13; github.com/mattermost/mattermost/server/v8 (Go) 8.0.0-20251015091448-abbf01b9db45; govulncheck-vulndb (openSUSE:Leap 15.6) 0.0.20251230T014957-150000.1.134.1.

Low priority for now. Upgrade to github.com/mattermost/mattermost-server (Go) 10.11.5, 10.12.2, 10.5.13; github.com/mattermost/mattermost/server/v8 (Go) 8.0.0-20251015091448-abbf01b9db45; govulncheck-vulndb (openSUSE:Leap 15.6) 0.0.20251230T014957-150000.1.134.1 or later.

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 11.0.x <= 11.0.2, 10.12.x <= 10.12.1, 10.11.x <= 10.11.4, 10.5.x <= 10.5.12 fail to sanitize team email addresses to be visible only to Team Admins, which allows any authenticated user to view team email addresses via the GET /api/v4/channels/{channel_id}/common_teams endpoint

Info leak

Published: Nov 27, 2025
Updated: Oct 19, 2026
EPSS: 0.2% · 14th percentile
CWE: CWE-200

Report tools

JSON

Action score

Monitor

Low priority for now.

CVSS: 17 / 40 · 4.3 / 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: 4.3; 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
A fix has been released

If any of these changes, we'll tell you in the daily email digest.

Is your version affected? Check it

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

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
- 11.1.0, 11.0.3, 10.12.2, 10.11.5, 10.5.13not affected
- 11.0.0 and later · up to and including 11.0.2affected · semver
- 10.12.0 and later · up to and including 10.12.1affected · semver
- 10.11.0 and later · up to and including 10.11.4affected · semver
- 10.5.0 and later · up to and including 10.5.12affected · semver

Affected versions · NVD (4)

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

mattermost mattermost server10.5.0 and later · before 10.5.13
mattermost mattermost server10.11.0 and later · before 10.11.5
mattermost mattermost server10.12.0 and later · before 10.12.2
mattermost mattermost server11.0.0 and later · before 11.0.3

Package-level exposure

OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.

Ecosystem	Package	Affected range	Fix
Go	github.com/mattermost/mattermost-server	from 0	—
Go	github.com/mattermost/mattermost-server	from 10.11.0 · before 10.11.5	10.11.5
Go	github.com/mattermost/mattermost-server	from 10.12.0 · before 10.12.2	10.12.2
Go	github.com/mattermost/mattermost-server	from 10.5.0 · before 10.5.13	10.5.13
Go	github.com/mattermost/mattermost-server	from 11.0.0 · before 11.0.3	11.0.3
Go	github.com/mattermost/mattermost-server/v5	from 0	—
Go	github.com/mattermost/mattermost-server/v6	from 0	—
Go	github.com/mattermost/mattermost/server/v8	before 8.0.0-20251015091448-abbf01b9db45	8.0.0-20251015091448-abbf01b9db45
openSUSE:Leap 15.6	govulncheck-vulndb	before 0.0.20251230T014957-150000.1.134.1	0.0.20251230T014957-150000.1.134.1

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.
39Monitor
CVE-2025-12421Account Takeover via Code Exchange Endpoint
39Monitor
CVE-2025-12419Account takeover on OAuth/OpenID-enabled servers
39Monitor

Published before and after this one in the same product

← EarlierCVE-2025-11794Nov 14, 2025 · Password hash and MFA secret returned in user email verification endpoint
19Monitor
← EarlierCVE-2025-55074Nov 18, 2025 · Channel member objects leak read status
14Monitor
Later →CVE-2025-12756Dec 1, 2025 · Insecure Direct Object Reference in Mattermost Boards Plugin Enables Unauthorised Comment Deletion
17Monitor

Remediation

Which version to upgrade to

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

Product / package	Fixed version	Source
Go:github.com/mattermost/mattermost-server	10.11.5	Package registry (OSV)
Go:github.com/mattermost/mattermost-server	10.12.2	Package registry (OSV)
Go:github.com/mattermost/mattermost-server	10.5.13	Package registry (OSV)
Go:github.com/mattermost/mattermost-server	11.0.3	Package registry (OSV)
Go:github.com/mattermost/mattermost/server/v8	8.0.0-20251015091448-abbf01b9db45	Package registry (OSV)
opensuse:govulncheck-vulndb	0.0.20251230T014957-150000.1.134.1 · openSUSE:Leap 15.6	Package registry (OSV)

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.

Credits

All researchers

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

hainguyen0207finder

Variant candidates

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

CVE-2026-6346172 days apartSensitive credentials exposed in plaintext in Mattermost support packets
34Monitor
CVE-2026-6347172 days apartMattermost Calls plugin exposes TURN server credentials in plaintext in support packets
30Monitor
CVE-2026-19621323 days apartMattermost leaks interactive-message integration secrets to non-admin users via post-deletion events and thread reads
26Monitor
CVE-2025-1382181 days apartUser profile update exposes password hash and MFA secrets
22Monitor
CVE-2026-6046197 days apartPlugin bot username conflict allows user account to be used as bot identity in Mattermost Server
21Monitor
CVE-2025-1179413 days apartPassword hash and MFA secret returned in user email verification endpoint
19Monitor

Bug bounty scope

Mattermost Public Bug Bounty Engagement Bugcrowd · paid · up to $2,000

The product’s vendor appears in a public program. Matched by name; verify the scope text in the program.

Not on record for this CVE: EPSS history · patch commit or PR link.

Technical details

Attack conditions

Anyone who can reach it over the internet can trigger it.
A low-privileged account is enough.
No user action is required.
No special conditions are required; it is repeatable.

If successful

Confidentiality: low · data can be read
Integrity: none
Availability: none

Attack vector: Network
Attack complexity: Low
Privileges required: Low
User interaction: None
Scope: Unchanged
Confidentiality impact: Low
Integrity impact: None
Availability impact: None

Weakness class (CWE)

CWE-200 · Exposure of Sensitive Information to an Unauthorized Actor

CVSS vector

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N

nvd-secondary

Root cause

The extension requests broader permissions than its function needs and sends the data it collects out for purposes beyond its stated function.

The bug in code

The whole CWE-200 class

A representative example of this vulnerability class. Not the vendor's source code; it shows the faulty pattern and its fix.

Vulnerable

json

1{
2  "permissions": ["tabs", "<all_urls>"],
3  "background": { "service_worker": "analytics.js" }
4}

Fixed

json

1{
2  "permissions": ["activeTab"],
3  "host_permissions": ["https://yildiz.example/*"]
4}

Attack context

MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.

Attack patterns (CAPEC)

ATT&CK techniques

Change log (1)

Fix✗ → ✓Sep 28, 2026, 10:47 PM UTC

For records you follow, these changes also arrive as notifications. →

References

mattermost.com/security-updates

Vendor advisories and official records. Exploit/PoC links are deliberately left out.

All records