Overview
CVE-2025-59480 is a medium-severity security vulnerability affecting Mattermost Mobile Apps versions 2.32.0 and earlier. This vulnerability arises from a failure to properly verify the origin of Single Sign-On (SSO) redirect tokens. A malicious Mattermost instance or an on-path attacker could exploit this flaw to obtain user session credentials by crafting malicious token-in-URL responses. This could lead to unauthorized access to user accounts and sensitive data.
Technical Details
The vulnerability stems from the Mattermost Mobile App’s insufficient validation of the SSO redirect URL. When a user authenticates with Mattermost through SSO, the application receives a token in a redirect URL. Versions up to and including 2.32.0 do not adequately verify that the redirect URL originates from the trusted Mattermost server configured in the app. This allows an attacker to set up a rogue Mattermost instance (or intercept traffic as an on-path attacker) and present a crafted redirect URL containing a malicious token. When the vulnerable mobile app processes this URL, it could inadvertently send the user’s session credentials to the attacker’s server.
Specifically, the vulnerable code section lacks robust checks to ensure the redirect URL’s hostname matches the expected Mattermost server’s hostname. An attacker can leverage this weakness by hosting a fake Mattermost instance and crafting a URL like:
https://evil-mattermost.com/oauth/callback?token=MALICIOUS_TOKEN
If a user opens this URL on a vulnerable Mattermost Mobile app, the app might process the MALICIOUS_TOKEN and potentially send sensitive data to evil-mattermost.com.
CVSS Analysis
The Common Vulnerability Scoring System (CVSS) provides a standardized way to assess the severity of security vulnerabilities. CVE-2025-59480 has a CVSS score of 6.1, indicating a MEDIUM severity. The CVSS vector string is not publicly available, but we can infer some elements based on the description.
Given the potential for credential theft, the likely CVSS vector elements include:
- Attack Vector (AV): Network (N)
- Attack Complexity (AC): High (H) – Requires either setting up a malicious server or performing a man-in-the-middle attack.
- Privileges Required (PR): None (N)
- User Interaction (UI): Required (R) – User must interact with the malicious link.
- Scope (S): Unchanged (U)
- Confidentiality Impact (C): High (H)
- Integrity Impact (I): None (N)
- Availability Impact (A): None (N)
A complete CVSS vector would be published alongside the vulnerability details by the Mattermost Security team in time.
Possible Impact
A successful exploitation of CVE-2025-59480 can have serious consequences:
- Account Compromise: Attackers can gain unauthorized access to user accounts, potentially reading private messages, accessing files, and impersonating users.
- Data Breach: Sensitive information shared within Mattermost channels could be exposed, leading to a data breach.
- Lateral Movement: In organizations where Mattermost is integrated with other systems, compromised accounts could be used to move laterally within the network.
- Reputational Damage: A successful attack could damage the reputation of the organization and erode trust in Mattermost as a secure communication platform.
Mitigation and Patch Steps
The primary mitigation for CVE-2025-59480 is to update your Mattermost Mobile Apps to a version greater than 2.32.0. Later versions include the necessary security fixes to properly validate SSO redirect tokens.
- Update Mobile Apps: Users should update their Mattermost Mobile Apps via the Google Play Store (Android) or the App Store (iOS).
- Educate Users: Inform users about the risks of clicking on suspicious links, especially those related to SSO logins.
- Monitor Network Traffic: Implement network monitoring to detect and block suspicious activity, such as connections to known malicious domains.
