Mattermost versions 11.2.x <= 11.2.2, 10.11.x <= 10.11.10, 11.4.x <= 11.4.0, 11.3.x <= 11.3.1 fail to sanitize user-controlled post content in the mmctl commands terminal output which allows attackers to manipulate administrator terminals via crafted messages containing ANSI and OSC escape sequences that enable screen manipulation, fake prompts, and clipboard hijacking.. Mattermost Advisory ID: MMSA-2026-00599

Mattermost versions 11.4.x <= 11.4.0, 11.3.x <= 11.3.1, 11.2.x <= 11.2.3, 10.11.x <= 10.11.11 fail to validate Advanced Logging file target paths which allows system administrators to read arbitrary host files via malicious AdvancedLoggingJSON configuration in support packet generation. Mattermost Advisory ID: MMSA-2025-00562

A flaw was found in Foreman. A remote attacker could exploit a command injection vulnerability in Foreman's WebSocket proxy implementation. This vulnerability arises from the system's use of unsanitized hostname values from compute resource providers when constructing shell commands. By operating a malicious compute resource server, an attacker could achieve remote code execution on the Foreman server when a user accesses VM VNC console functionality. This could lead to the compromise of sensitive credentials and the entire managed infrastructure.

Ory Polis, formerly known as BoxyHQ Jackson, bridges or proxies a SAML login flow to OAuth 2.0 or OpenID Connect. Versions prior to 26.2.0 contain a DOM-based Cross-Site Scripting (XSS) vulnerability in Ory Polis's login functionality. The application improperly trusts a URL parameter (`callbackUrl`), which is passed to `router.push`. An attacker can craft a malicious link that, when opened by an authenticated user (or an unauthenticated user that later logs in), performs a client-side redirect and executes arbitrary JavaScript in the context of their browser. This could lead to credential theft, internal network pivoting, and unauthorized actions performed on behalf of the victim. Version 26.2.0 contains a patch for the issue.

A flaw was found in polkit. A local user can exploit this by providing a specially crafted, excessively long input to the `polkit-agent-helper-1` setuid binary via standard input (stdin). This unbounded input can lead to an out-of-memory (OOM) condition, resulting in a Denial of Service (DoS) for the system.

A flaw was found in libsoup's SoupServer. A remote attacker could exploit a use-after-free vulnerability where the `soup_server_disconnect()` function frees connection objects prematurely, even if a TLS handshake is still pending. If the handshake completes after the connection object has been freed, a dangling pointer is accessed, leading to a server crash and a Denial of Service.

Mattermost Plugins versions <=11.4 11.0.4 11.1.3 11.3.2 10.11.11.0 fail to validate incoming request size which allows an authenticated attacker to cause service disruption via the webhook endpoint. Mattermost Advisory ID: MMSA-2026-00589

A flaw was found in p11-kit. A remote attacker could exploit this vulnerability by calling the C_DeriveKey function on a remote token with specific IBM kyber or IBM btc derive mechanism parameters set to NULL. This could lead to the RPC-client attempting to return an uninitialized value, potentially resulting in a NULL dereference or undefined behavior. This issue may cause an application level denial of service or other unpredictable system states.

A flaw was found in libssh in which a malicious SFTP (SSH File Transfer Protocol) server can exploit this by sending a malformed 'longname' field within an `SSH_FXP_NAME` message during a file listing operation. This missing null check can lead to reading beyond allocated memory on the heap. This can cause unexpected behavior or lead to a denial of service (DoS) due to application crashes.

Mattermost Plugins versions <=11.4 10.11.11.0 fail to validate webhook request timestamps which allows an attacker to corrupt Zoom meeting state in Mattermost via replayed webhook requests. Mattermost Advisory ID: MMSA-2026-00584