CVE-2026-22892: Mattermost Server Auth Bypass Vulnerability

CVE-2026-22892 Overview

CVE-2026-22892 is an improper authorization vulnerability in Mattermost Server that allows authenticated attackers to bypass channel access controls through the Jira plugin integration. The vulnerability exists because Mattermost fails to validate user permissions when creating Jira issues from posts, enabling attackers with access to the Jira plugin to read post content and attachments from channels they do not have access to via the /create-issue API endpoint.

Critical Impact
Authenticated attackers can exfiltrate sensitive post content and attachments from private channels by exploiting the Jira plugin's /create-issue endpoint, potentially exposing confidential business communications.

Affected Products

Mattermost Server versions 11.1.x through 11.1.2
Mattermost Server versions 10.11.x through 10.11.9
Mattermost Server versions 11.2.x through 11.2.1

Discovery Timeline

2026-02-13 - CVE CVE-2026-22892 published to NVD
2026-02-18 - Last updated in NVD database

Technical Details for CVE-2026-22892

Vulnerability Analysis

This vulnerability is classified as CWE-863 (Incorrect Authorization), a critical weakness where an application fails to properly verify that a user is authorized to access a resource or perform an action. In the context of Mattermost's Jira plugin integration, the application accepts post IDs as input when creating Jira issues but neglects to verify whether the requesting user has legitimate access to the channel containing the referenced post.

The exploitation mechanism is straightforward: an authenticated user with access to the Jira plugin can craft API requests to the /create-issue endpoint, supplying arbitrary post IDs. Since the authorization check is missing, the server processes these requests and returns the post content and any associated attachments, regardless of channel membership or permissions.

Root Cause

The root cause lies in insufficient authorization checks within the Jira plugin's issue creation workflow. When a user submits a request to create a Jira issue from a Mattermost post, the backend logic retrieves the post content based solely on the provided post ID without validating whether the requesting user belongs to the channel where the post originated. This creates a direct object reference vulnerability where knowledge of a post ID is sufficient to access its contents.

Attack Vector

The attack is network-accessible and requires low-privilege authenticated access to a Mattermost instance with the Jira plugin enabled. An attacker can enumerate or guess post IDs (which may follow predictable patterns) and submit them to the /create-issue API endpoint. The server responds with the post content and metadata, effectively bypassing all channel-level access controls.

The attack flow involves an authenticated user making POST requests to the Jira plugin's create-issue endpoint with target post IDs. Since Mattermost's post IDs are typically UUIDs or sequential identifiers, an attacker could iterate through possible values or leverage other information disclosure vectors to obtain valid post IDs from restricted channels. See the Mattermost Security Updates page for additional technical details.

Detection Methods for CVE-2026-22892

Indicators of Compromise

Unusual volume of /create-issue API requests from individual user accounts
Jira issue creation attempts referencing posts from channels the requesting user is not a member of
Access log entries showing repeated failed or successful post retrievals across multiple channels
Anomalous patterns of post ID enumeration in API request logs

Detection Strategies

Monitor Mattermost server logs for /create-issue endpoint requests and correlate with user channel membership
Implement alerting on high-frequency Jira plugin API calls from single user sessions
Review audit logs for users accessing posts from channels outside their membership scope
Deploy application-layer monitoring to detect sequential or pattern-based post ID enumeration

Monitoring Recommendations

Enable verbose logging for the Jira plugin integration component
Configure SIEM rules to correlate Jira issue creation events with channel access permissions
Monitor for unusual spikes in API activity targeting the /create-issue endpoint
Establish baseline metrics for normal Jira plugin usage patterns to identify anomalous behavior

How to Mitigate CVE-2026-22892

Immediate Actions Required

Upgrade Mattermost Server to patched versions: 11.1.3+, 10.11.10+, or 11.2.2+ as applicable
Review server logs for evidence of unauthorized post access via the Jira plugin
Temporarily disable the Jira plugin if immediate patching is not feasible
Audit Jira plugin access permissions and restrict to essential users only

Patch Information

Mattermost has released security patches addressing this vulnerability as documented in advisory MMSA-2025-00550. Organizations should upgrade to the latest patched versions available from Mattermost. For detailed patch information and download links, refer to the Mattermost Security Updates page.

Workarounds

Disable the Jira plugin entirely until patches can be applied
Restrict Jira plugin access to a minimal set of trusted users via System Console settings
Implement network-level controls to limit access to Mattermost API endpoints
Consider deploying a web application firewall (WAF) rule to filter /create-issue requests with suspicious patterns

bash

# Disable Jira plugin via Mattermost System Console CLI
mattermost plugin disable jira