CVE-2026-49256 Discourse: Hidden tag names leaked via category serializers

What is CVE-2026-49256?

CVE-2026-49256 is a medium-severity vulnerability in Discourse Discourse, published on 9 Jul 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

Official description

Discourse is an open-source discussion platform. Prior to 2026.6.0, 2026.5.1, 2026.4.2, and 2026.1.5, restricted tag and tag-group names attached to publicly readable categories as allowed_tags, allowed_tag_groups, or required tag groups could leak to anonymous and unauthorized users through category and group endpoints. This issue is fixed in versions 2026.6.0, 2026.5.1, 2026.4.2, and 2026.1.5.

Weakness: CWE-200

Which versions are affected by CVE-2026-49256?

1 open source package ship an affected version, including discourse. It affects 1 product.

Products include Discourse Discourse.

How do I fix CVE-2026-49256?

Upgrade discourse to a fixed version for your release line: 2026.1.5, 2026.4.2 or 2026.5.1.

Is CVE-2026-49256 being exploited?

There is no known exploitation of CVE-2026-49256 in the wild and no public exploit code.

Other vulnerabilities in Discourse Discourse

• CVE-2021-41163 RCE via malicious SNS subscription payload Critical 10.0
• CVE-2022-36066 Discourse vulnerable to RCE via admins uploading maliciously zipped file Critical 9.1
• CVE-2022-39356 Discourse user account takeover via email and invite link High 8.9
• CVE-2023-22468 Discourse vulnerable to Cross-site Scripting in local oneboxes High 8.8
• CVE-2026-27934 Discourse leaks private topic title and post excerpt via user action API endpoint High 8.7

All Discourse Discourse vulnerabilities

Sources

• CVE record
• NVD
• OSV
• GitHub advisory
• How this page is made

Also known as BIT-discourse-2026-49256, GHSA-mwp7-572g-6qpx.