CVE-2026-6673
Mattermost Jira plugin had unauthenticated {{/ac/installed}} lifecycle callback during pending Jira Cloud install
Description
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
INFO
Published Date :
June 22, 2026, 2:17 p.m.
Last Modified :
June 23, 2026, 8:49 p.m.
Remotely Exploit :
Yes !
Source :
[email protected]
Affected Products
The following products are affected by CVE-2026-6673
vulnerability.
Even if cvefeed.io is aware of the exact versions of the
products
that
are
affected, the information is not represented in the table below.
CVSS Scores
| Score | Version | Severity | Vector | Exploitability Score | Impact Score | Source |
|---|---|---|---|---|---|---|
| CVSS | 134c704f-9b21-4f2e-91b3-4a467353bcc0 | |||||
| CVSS 3.1 | MEDIUM | 9302f53e-dde5-4bf3-b2f2-a83f91ac0eee | ||||
| CVSS 3.1 | MEDIUM | MITRE-CVE | ||||
| CVSS 3.1 | MEDIUM | [email protected] |
Solution
- Update Mattermost to the latest version.
- Verify Atlassian Connect integration functionality.
- Monitor integration logs for suspicious activity.
References to Advisories, Solutions, and Tools
Here, you will find a curated list of external links that provide in-depth
information, practical solutions, and valuable tools related to
CVE-2026-6673.
| URL | Resource |
|---|---|
| https://mattermost.com/security-updates | Vendor Advisory |
CWE - Common Weakness Enumeration
While CVE identifies
specific instances of vulnerabilities, CWE categorizes the common flaws or
weaknesses that can lead to vulnerabilities. CVE-2026-6673 is
associated with the following CWEs:
Common Attack Pattern Enumeration and Classification (CAPEC)
Common Attack Pattern Enumeration and Classification
(CAPEC)
stores attack patterns, which are descriptions of the common attributes and
approaches employed by adversaries to exploit the CVE-2026-6673
weaknesses.
We scan GitHub repositories to detect new proof-of-concept exploits. Following list is a collection of public exploits and proof-of-concepts, which have been published on GitHub (sorted by the most recently updated).
Results are limited to the first 15 repositories due to potential performance issues.
The following list is the news that have been mention
CVE-2026-6673 vulnerability anywhere in the article.
The following table lists the changes that have been made to the
CVE-2026-6673 vulnerability over time.
Vulnerability history details can be useful for understanding the evolution of a vulnerability, and for identifying the most recent changes that may impact the vulnerability's severity, exploitability, or other characteristics.
-
Initial Analysis by [email protected]
Jun. 23, 2026
Action Type Old Value New Value Added CPE Configuration OR *cpe:2.3:a:mattermost:mattermost_server:*:*:*:*:*:*:*:* versions from (including) 10.11.0 up to (excluding) 10.11.18 *cpe:2.3:a:mattermost:mattermost_server:*:*:*:*:*:*:*:* versions from (including) 11.7.0 up to (excluding) 11.7.1 *cpe:2.3:a:mattermost:mattermost_server:*:*:*:*:*:*:*:* versions from (including) 11.5.0 up to (excluding) 11.5.6 *cpe:2.3:a:mattermost:mattermost_server:*:*:*:*:*:*:*:* versions from (including) 11.6.0 up to (excluding) 11.6.3 Added Reference Type Mattermost, Inc.: https://mattermost.com/security-updates Types: Vendor Advisory -
CVE Modified by 134c704f-9b21-4f2e-91b3-4a467353bcc0
Jun. 22, 2026
Action Type Old Value New Value Added SSVC {'id': 'CVE-2026-6673', 'role': 'CISA Coordinator', 'options': [{'exploitation': 'none'}, {'automatable': 'no'}, {'technicalImpact': 'partial'}], 'version': '2.0.3', 'timestamp': '2026-06-22T15:40:53.578692Z'} -
New CVE Received by [email protected]
Jun. 22, 2026
Action Type Old Value New Value Added Affected [{'vendor': 'Mattermost', 'product': 'Mattermost', 'versions': [{'status': 'affected', 'version': '11.7.0', 'versionType': 'semver', 'lessThanOrEqual': '11.7.0'}, {'status': 'affected', 'version': '11.6.0', 'versionType': 'semver', 'lessThanOrEqual': '11.6.2'}, {'status': 'affected', 'version': '11.5.0', 'versionType': 'semver', 'lessThanOrEqual': '11.5.5'}, {'status': 'affected', 'version': '10.11.0', 'versionType': 'semver', 'lessThanOrEqual': '10.11.17'}, {'status': 'unaffected', 'version': '11.8.0'}, {'status': 'unaffected', 'version': '11.7.1'}, {'status': 'unaffected', 'version': '11.6.3'}, {'status': 'unaffected', 'version': '11.5.6'}, {'status': 'unaffected', 'version': '10.11.18'}], 'defaultStatus': 'unaffected'}] Added Description 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 Added CVSS V3.1 AV:N/AC:H/PR:L/UI:R/S:U/C:N/I:H/A:H Added CWE CWE-306 Added Reference https://mattermost.com/security-updates