Communication and Collaboration

In Mattermost Plugins versions <=2.1.3.0 medium severity vulnerability CVE-2026-24661 was detected. This vulnerability allows attackers to cause memory exhaustion and denial of service by sending an oversized JSON payload to the {{/changes}} webhook endpoint. To address this issue users must upgrade to the 2.3.2.0 version. For more details, visit https://nvd.nist.gov/vuln/detail/CVE-2026-24661.

In Discourse versions 2026.1.0-latest to before 2026.1.3, 2026.2.0-latest to before 2026.2.2, and 2026.3.0-latest to before 2026.3.0 a low severity vulnerability CVE-2026-34947 was detected. This vulnerability allows attackers to access staged user custom fields and usernames on public invite pages without email verification, leading to unintended information disclosure. To address this issue, users should upgrade Discourse to versions 2026.1.3, 2026.2.2 , or 2026.3.0. For more details, visit https://nvd.nist.gov/vuln/detail/CVE-2026-34947.

In Discourse versions 2026.1.0-latest to before 2026.1.3, 2026.2.0-latest to before 2026.2.2, and 2026.3.0-latest to before 2026.3.0 a medium severity vulnerability CVE-2026-27481 was detected. This vulnerability allows unauthenticated or unauthorized users to view hidden staff-only tags and associated data due to an authorization bypass in tag routes. To address this issue, users should upgrade Discourse to versions 2026.1.3, 2026.2.2, or 2026.3.0. For more details, visit https://nvd.nist.gov/vuln/detail/CVE-2026-27481.

In Discourse versions 2026.1.0-latest to before 2026.1.3, 2026.2.0-latest to before 2026.2.2, and 2026.3.0-latest to before 2026.3.0 a medium severity vulnerability CVE-2026-33300 was detected. This vulnerability allows moderators to access hidden group names and user count metadata via the category-chatables endpoint due to an authorization bypass in the controller’s show action. To address this issue, users should upgrade Discourse to versions 2026.1.3, 2026.2.2, or 2026.3.0. For more details, visit https://nvd.nist.gov/vuln/detail/CVE-2026-33300.

In Discourse versions 2026.1.0-latest to before 2026.1.3, 2026.2.0-latest to before 2026.2.2, and 2026.3.0-latest to before 2026.3.0 a medium severity vulnerability CVE-2026-33185 was detected. This vulnerability allows attackers to perform server-side request forgery (SSRF) by abusing the group email settings test endpoint to initiate outbound connections to arbitrary hosts and ports, potentially enabling internal network probing. To address this issue, users should upgrade Discourse to versions 2026.1.3, 2026.2.2, or 2026.3.0. For more details, visit https://nvd.nist.gov/vuln/detail/CVE-2026-33185.

In Discourse versions 2026.1.0-latest to before 2026.1.3, 2026.2.0-latest to before 2026.2.2, and 2026.3.0-latest to before 2026.3.0 a medium severity vulnerability CVE-2026-33415 was detected. This vulnerability allows authenticated moderator-level users to access post content, topic titles, and usernames from categories they are not authorized to view due to improper access control in a sentiment analytics endpoint. To address this issue, users should upgrade Discourse to versions 2026.1.3, 2026.2.2, or 2026.3.0. For more details, visit https://nvd.nist.gov/vuln/detail/CVE-2026-33415.

In Mattermost versions 11.3.x <= 11.3.0, 11.2.x <= 11.2.2, and 10.11.x <= 10.11.10 a medium severity vulnerability CVE-2026-2457 was detected. This vulnerability allows authenticated attackers to spoof permalink embeds and impersonate other users by submitting crafted metadata through the post update API endpoint due to insufficient sanitization of client-supplied input. To address this issue, users should upgrade Mattermost to versions 11.4.0, 11.3.1, 11.2.3 or 10.11.11. For more details, visit https://nvd.nist.gov/vuln/detail/CVE-2026-2457.

In Mattermost versions 11.3.x <= 11.3.0, 11.2.x <= 11.2.2, and 10.11.x <= 10.11.10 a medium severity vulnerability CVE-2026-2456 was detected. This vulnerability allows authenticated attackers to cause server memory exhaustion and denial of service (DoS) by leveraging a malicious integration server that returns excessively large responses from integration action endpoints. To address this issue, users should upgrade Mattermost to versions 11.4.0, 11.3.1, 11.2.3 or 10.11.11. For more details, visit https://nvd.nist.gov/vuln/detail/CVE-2026-2456.

In Mattermost versions 11.3.x <= 11.3.0, 11.2.x <= 11.2.2, and 10.11.x <= 10.11.10 a medium severity vulnerability CVE-2026-2455 was detected. This vulnerability allows attackers to perform server-side request forgery (SSRF) attacks against internal services by exploiting improper canonicalization of IPv4-mapped IPv6 addresses during reserved IP validation. To address this issue, users should upgrade Mattermost to versions 11.4.0, 11.3.1, 11.2.3 or 10.11.11. For more details, visit https://nvd.nist.gov/vuln/detail/CVE-2026-2455.