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NVD / CVE Program· CNA Mattermost

CVE-2026-6673: Mattermost Jira plugin had unauthenticated {{/ac/installed}} lifecycle callback during pending Jira Cloud install

Noroxi assessment

Priority: Monitor (action score 25/100)

  • 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: 0.29% (FIRST EPSS).
  • Anyone who can reach it over the internet can trigger it. A low-privileged account is enough. A user must open a link or visit a page. Special conditions such as timing or configuration are required.
  • Fixed version: github.com/mattermost/mattermost-server (Go) 10.11.18, 10.11.18+incompatible, 11.5.6.

Low priority for now. Upgrade to github.com/mattermost/mattermost-server (Go) 10.11.18, 10.11.18+incompatible, 11.5.6 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 11.7.x <= 11.7.0, 11.6.x <= 11.6.2, 11.5.x <= 11.5.5, 10.11.x <= 10.11.17 fail to authenticate Atlassian Connect installed callbacks, allowing a remote unauthenticated attacker to inject a rogue sharedSecret and disrupt the Jira integration via POST to /ac/installed during the pending-install window.. Mattermost Advisory ID: MMSA-2026-00654

MediumCVSS 6.4 · v3.1—No exploit Fix available
Published
Jun 22, 2026
Updated
Jun 23, 2026
EPSS
0.2% · 22th percentile

Report tools

JSON

Action score

25

Monitor

Low priority for now.

CVSS
25 / 40 · 6.4 / 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
6.4
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-2026-6673

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 10.11.18
  • mattermost mattermost server11.5.0 and later · before 11.5.6
  • mattermost mattermost server11.6.0 and later · before 11.6.3
  • mattermost mattermost server11.7.0 and later · before 11.7.1

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, 11.7.1, 11.6.3, 11.5.6, 10.11.18not affected
    • 11.7.0 and later · up to and including 11.7.0affected · semver
    • 11.6.0 and later · up to and including 11.6.2affected · semver
    • 11.5.0 and later · up to and including 11.5.5affected · semver
    • 10.11.0 and later · up to and including 10.11.17affected · semver

Package-level exposure

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

EcosystemPackageAffected rangeFix
Gogithub.com/mattermost/mattermost-serverfrom 10.11.0 · before 10.11.1810.11.18
Gogithub.com/mattermost/mattermost-serverfrom 10.11.0+incompatible · before 10.11.18+incompatible10.11.18+incompatible
Gogithub.com/mattermost/mattermost-serverfrom 11.5.0 · before 11.5.611.5.6
Gogithub.com/mattermost/mattermost-serverfrom 11.5.0+incompatible · before 11.5.6+incompatible11.5.6+incompatible
Gogithub.com/mattermost/mattermost-serverfrom 11.6.0 · before 11.6.311.6.3
Gogithub.com/mattermost/mattermost-serverfrom 11.6.0+incompatible · before 11.6.3+incompatible11.6.3+incompatible
Gogithub.com/mattermost/mattermost-serverfrom 11.7.0 · before 11.7.111.7.1
Gogithub.com/mattermost/mattermost-serverfrom 11.7.0+incompatible · before 11.7.1+incompatible11.7.1+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-2026-5139Jun 22, 2026 · GitLab Plugin Allows Non-Admin Users to Modify Default Instance Configuration
    21Monitor
  • ← EarlierCVE-2026-6062Jun 22, 2026 · IDOR in Jira plugin subscription edit endpoint
    25Monitor
  • Later →CVE-2026-8074Jun 22, 2026 · Improper Permission Check Allows User Manager to Deactivate Bot Accounts
    15Monitor

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-server10.11.18Package registry (OSV)
Go:github.com/mattermost/mattermost-server10.11.18+incompatiblePackage registry (OSV)
Go:github.com/mattermost/mattermost-server11.5.6Package registry (OSV)
Go:github.com/mattermost/mattermost-server11.5.6+incompatiblePackage registry (OSV)
Go:github.com/mattermost/mattermost-server11.6.3Package registry (OSV)
Go:github.com/mattermost/mattermost-server11.6.3+incompatiblePackage registry (OSV)
Go:github.com/mattermost/mattermost-server11.7.1Package registry (OSV)
Go:github.com/mattermost/mattermost-server11.7.1+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.

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.

Variant candidates

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

  • CVE-2025-25068458 days apartBypassing MFA Enforcement on Plugin Endpoints
    35Monitor
  • CVE-2025-55070220 days apartLack of MFA enforcement in WebSocket connections
    30Monitor
  • CVE-2025-6226339 days apartIDOR in CreatePost API allows for timeboxed message disclosure
    26Monitor
  • CVE-2025-55073220 days apartMS Teams plugin OAuth allows editing arbitrary posts
    21Monitor
  • CVE-2025-13870202 days apartUnauthorized access and subscription vulnerability in Boards
    17Monitor
  • CVE-2025-47870305 days apartTeam invite ID leaked to team admin with no member invite privileges
    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.

  • CVE-2026-485832 days apartPath traversal in integration action URL leading to arbitrary API execution via system admin’s auth token.
    39Monitor
  • CVE-2026-696110 days apartCVE-2026-6961: Path traversal via unsanitized FileInfo.Name in Mattermost federation sync
    30Monitor
  • CVE-2026-43394 days apartSSRF via unvalidated attachment URLs in Mattermost Agents plugin MCP server
    26Monitor
  • CVE-2026-633335 days apartSSRF via Host Header Spoofing in Custom Slash Commands
    20Monitor

Bug bounty scope

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

Technical details

Attack conditions

  • Anyone who can reach it over the internet can trigger it.
  • A low-privileged account is enough.
  • A user must open a link or visit a page.
  • Special conditions such as timing or configuration are required.

If successful

Confidentiality
none
Integrity
high · data or configuration can be modified
Availability
high · the service can be disrupted
Attack vector
Network
Attack complexity
High
Privileges required
Low
User interaction
Required
Scope
Unchanged
Confidentiality impact
None
Integrity impact
High
Availability impact
High

Weakness class (CWE)

CWE-306 · Missing Authentication for Critical Function

CVSS vector

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

nvd-secondary

Root cause

A function added for development or support ships to production without authentication. It often relies on the assumption that it is “only reachable from the internal network.”

The bug in code

The whole CWE-306 class

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

Vulnerable

ts
// Added for the support teamapp.post("/maintenance/reset", resetDevice);

Fixed

ts
if (config.maintenanceEnabled) {  app.post(    "/maintenance/reset",    requireSession, requireRole("admin"), resetDevice  );}

Attack context

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

ATT&CK techniques

—

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