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NVD / CVE Program· CNA Mattermost

CVE-2026-6347: Mattermost Calls plugin exposes TURN server credentials in plaintext in support packets

Noroxi assessment

Priority: Monitor (action score 30/100)

  • 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: 0.26% (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.
  • Fixed version: github.com/mattermost/mattermost-plugin-calls (Go) 1.12.0-rc2; github.com/mattermost/mattermost-server (Go) 10.11.14, 10.11.14+incompatible, 11.4.4.
  • Mentioned 1 time in Turkish national cyber security advisories (siberguvenlik.gov.tr).

Low priority for now. Upgrade to github.com/mattermost/mattermost-plugin-calls (Go) 1.12.0-rc2; github.com/mattermost/mattermost-server (Go) 10.11.14, 10.11.14+incompatible, 11.4.4 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 11.5.x <= 11.5.1, 10.11.x <= 10.11.13, 11.4.x <= 11.4.3 fail to sanitize sensitive configuration fields in the Mattermost Calls plugin which allows an attacker with access to a support packet to obtain TURN server credentials via the plaintext values present in the exported plugin configuration.. Mattermost Advisory ID: MMSA-2026-00605

HighCVSS 7.6 · v3.1—No exploit Fix available
Published
May 18, 2026
Updated
Oct 14, 2026
EPSS
0.2% · 18th percentile

Report tools

JSON

Action score

30

Monitor

Low priority for now.

CVSS
30 / 40 · 7.6 / 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
7.6
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.

Follow CVE-2026-6347

When you'll hear from us

  • when it enters CISA KEV
  • when exploit code appears or is weaponized
  • when the record is updated (including a fixed version)
  • when EPSS rises 20 points in a week

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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.

VendorProduct
mattermostmattermost 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 10.11.14
  • mattermost mattermost server11.4.0 and later · before 11.4.4
  • mattermost mattermost server11.5.0 and later · before 11.5.2

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

    • 11.6.0, 11.5.2, 10.11.14, 11.4.4not affected
    • 11.5.0 and later · up to and including 11.5.1affected · semver
    • 10.11.0 and later · up to and including 10.11.13affected · semver
    • 11.4.0 and later · up to and including 11.4.3affected · semver

Package-level exposure

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

EcosystemPackageAffected rangeFix
Gogithub.com/mattermost/mattermost-plugin-callsbefore 1.12.0-rc21.12.0-rc2
Gogithub.com/mattermost/mattermost-serverfrom 10.11.0 · before 10.11.1410.11.14
Gogithub.com/mattermost/mattermost-serverfrom 10.11.0+incompatible · before 10.11.14+incompatible10.11.14+incompatible
Gogithub.com/mattermost/mattermost-serverfrom 11.4.0 · before 11.4.411.4.4
Gogithub.com/mattermost/mattermost-serverfrom 11.4.0+incompatible · before 11.4.4+incompatible11.4.4+incompatible
Gogithub.com/mattermost/mattermost-serverfrom 11.5.0 · before 11.5.211.5.2
Gogithub.com/mattermost/mattermost-serverfrom 11.5.0+incompatible · before 11.5.2+incompatible11.5.2+incompatible

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-2026-6345May 18, 2026 · Prevent password disclosure and force reset during Slack import
    26Monitor
  • ← EarlierCVE-2026-6346May 18, 2026 · Sensitive credentials exposed in plaintext in Mattermost support packets
    34Monitor
  • Later →CVE-2026-4055May 21, 2026 · Insufficient permission validation on cross-team playbook run creation
    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 / packageFixed versionSource
Go:github.com/mattermost/mattermost-plugin-calls1.12.0-rc2Package registry (OSV)
Go:github.com/mattermost/mattermost-server10.11.14Package registry (OSV)
Go:github.com/mattermost/mattermost-server10.11.14+incompatiblePackage registry (OSV)
Go:github.com/mattermost/mattermost-server11.4.4Package registry (OSV)
Go:github.com/mattermost/mattermost-server11.4.4+incompatiblePackage registry (OSV)
Go:github.com/mattermost/mattermost-server11.5.2Package registry (OSV)
Go:github.com/mattermost/mattermost-server11.5.2+incompatiblePackage 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.

No history yet (it accumulates with the daily EPSS job).

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.

Variant candidates

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

  • CVE-2026-63460 days apartSensitive credentials exposed in plaintext in Mattermost support packets
    34Monitor
  • CVE-2026-19621151 days apartMattermost leaks interactive-message integration secrets to non-admin users via post-deletion events and thread reads
    26Monitor
  • CVE-2025-1382191 days apartUser profile update exposes password hash and MFA secrets
    22Monitor
  • CVE-2026-604625 days apartPlugin bot username conflict allows user account to be used as bot identity in Mattermost Server
    21Monitor
  • CVE-2025-11794185 days apartPassword hash and MFA secret returned in user email verification endpoint
    19Monitor
  • CVE-2026-36364 days apartSanitize team member data returned by API
    17Monitor

Chain candidates

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

—

Bug bounty scope

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

National notice (Türkiye Cybersecurity Directorate / USOM)

Official security notices citing this record; remediation advice is on the agency's page.

All national notices →

Technical details

Attack conditions

  • 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.

If successful

Confidentiality
high · data can be read
Integrity
none
Availability
low · the service can be disrupted

Impact can extend beyond the vulnerable component (scope changes).

Attack vector
Network
Attack complexity
Low
Privileges required
High
User interaction
None
Scope
Changed
Confidentiality impact
High
Integrity impact
None
Availability impact
Low

Weakness class (CWE)

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

CVSS vector

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

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

Fixed

json
{  "permissions": ["activeTab"],  "host_permissions": ["https://yildiz.example/*"]}

Attack context

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

Change log

  1. Fix✗ → ✓

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

References

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

All records