CVE-2025-14273: Mattermost Server Auth Bypass Vulnerability

CVE-2025-14273 Overview

CVE-2025-14273 is an authentication bypass vulnerability affecting multiple versions of Mattermost Server with the Jira plugin enabled. The vulnerability stems from a failure to properly enforce authentication and issue-key path restrictions in the Jira plugin, allowing unauthenticated attackers who know a valid user ID to issue authenticated GET and POST requests to the Jira server via crafted plugin payloads that spoof the user ID and inject arbitrary issue key paths.

Critical Impact

This vulnerability enables unauthenticated attackers to perform authenticated actions on Jira servers by spoofing user identities, potentially leading to unauthorized data access, modification, or exfiltration of sensitive project information.

Affected Products

• Mattermost Server versions 11.1.x <= 11.1.0
• Mattermost Server versions 11.0.x <= 11.0.5
• Mattermost Server versions 10.12.x <= 10.12.3
• Mattermost Server versions 10.11.x <= 10.11.7
• Mattermost Jira plugin versions <= 4.4.0

Discovery Timeline

• 2025-12-22 - CVE-2025-14273 published to NVD
• 2025-12-29 - Last updated in NVD database

Technical Details for CVE-2025-14273

Vulnerability Analysis

This authentication bypass vulnerability (CWE-303: Incorrect Implementation of Authentication Algorithm) exists in the Mattermost Jira plugin integration. The plugin fails to properly validate authentication tokens and does not adequately restrict access to issue-key paths, creating a security gap that allows unauthorized access to Jira server functionality.

The flaw enables attackers to craft malicious payloads that bypass the intended authentication mechanisms. By knowing a valid user ID within the Mattermost system, an attacker can construct requests that appear to originate from that legitimate user, effectively impersonating them when communicating with the connected Jira server.

The vulnerability has a changed scope impact, meaning successful exploitation can affect resources beyond the vulnerable component itself—in this case, the connected Jira server and its data.

Root Cause

The root cause lies in the incorrect implementation of the authentication algorithm within the Mattermost Jira plugin. The plugin does not properly verify that requests originate from authenticated sessions, and it fails to validate that the user ID included in plugin payloads corresponds to the actual authenticated user making the request. Additionally, the lack of proper path restrictions on issue-key endpoints allows attackers to inject arbitrary paths into their requests.

Attack Vector

The attack vector is network-based, requiring no authentication and no user interaction. An attacker with knowledge of a valid Mattermost user ID can exploit this vulnerability remotely by:

1. Crafting malicious plugin payloads that include a spoofed user ID
2. Injecting arbitrary issue-key paths into the request
3. Sending these crafted requests to the vulnerable Mattermost server
4. The server processes the request as if it came from the spoofed user, forwarding authenticated requests to the Jira server

The vulnerability allows both GET and POST request methods, enabling attackers to both read sensitive information and potentially modify data on the connected Jira server.

Detection Methods for CVE-2025-14273

Indicators of Compromise

• Unusual Jira API requests originating from the Mattermost server with unexpected user ID patterns
• Requests to the Jira plugin endpoint from unauthenticated sessions or unexpected IP addresses
• Anomalous issue-key path patterns in Jira plugin requests that don't match typical user behavior
• Increased volume of Jira requests from specific Mattermost user IDs without corresponding user activity

Detection Strategies

• Monitor Mattermost server logs for Jira plugin requests that lack proper session authentication
• Implement alerting on Jira API requests that contain unusual or malformed issue-key paths
• Cross-reference Mattermost user activity logs with Jira request logs to identify discrepancies
• Deploy network monitoring to detect crafted payloads targeting the Jira plugin endpoints

Monitoring Recommendations

• Enable detailed logging for the Mattermost Jira plugin to capture all incoming requests and authentication states
• Configure SIEM rules to correlate Mattermost authentication events with Jira API activity
• Implement rate limiting and anomaly detection on Jira plugin endpoints
• Review Jira audit logs for actions performed via the Mattermost integration that don't align with expected user behavior

How to Mitigate CVE-2025-14273

Immediate Actions Required

• Update Mattermost Server to a patched version: 11.1.1+, 11.0.6+, 10.12.4+, or 10.11.8+
• Update the Mattermost Jira plugin to version 4.4.1 or later
• If immediate patching is not possible, consider temporarily disabling the Jira plugin integration
• Review Jira audit logs for any suspicious activity that may indicate prior exploitation

Patch Information

Mattermost has released security patches addressing this vulnerability under advisory MMSA-2025-00555. Organizations should apply the latest available updates for their respective version branches. Detailed patch information and download links are available at the Mattermost Security Updates page.

Workarounds

• Temporarily disable the Mattermost Jira plugin until patches can be applied
• Implement network-level access controls to restrict which systems can reach the Mattermost server's Jira plugin endpoints
• Configure firewall rules to limit access to the Mattermost server from trusted networks only
• Enable additional authentication layers such as VPN requirements for accessing the Mattermost instance

# Disable the Jira plugin via Mattermost CLI (temporary workaround)
./mattermost plugin disable com.mattermost.jira

# Verify the plugin is disabled
./mattermost plugin list