Discourse up to 2025.12.1/2026.1.0 authorization

Summaryinfo

A vulnerability categorized as problematic has been discovered in Discourse up to 2025.12.1/2026.1.0. Affected is an unknown function. The manipulation results in authorization. This vulnerability is identified as CVE-2026-26078. The attack can be executed remotely. There is not any exploit available. It is advisable to upgrade the affected component.

Detailsinfo

A vulnerability, which was classified as problematic, was found in Discourse up to 2025.12.1/2026.1.0. Affected is an unknown functionality. The manipulation with an unknown input leads to a authorization vulnerability. CWE is classifying the issue as CWE-639. The system's authorization functionality does not prevent one user from gaining access to another user's data or record by modifying the key value identifying the data. This is going to have an impact on integrity. CVE summarizes:

Discourse is an open source discussion platform. Prior to versions 2025.12.2, 2026.1.1, and 2026.2.0, when the `patreon_webhook_secret` site setting is blank, an attacker can forge valid webhook signatures by computing an HMAC-MD5 with an empty string as the key. Since the request body is known to the sender, the attacker can produce a matching signature and send arbitrary webhook payloads. This allows unauthorized creation, modification, or deletion of Patreon pledge data and triggering patron-to-group synchronization. This vulnerability is patched in versions 2025.12.2, 2026.1.1, and 2026.2.0. The fix rejects webhook requests when the webhook secret is not configured, preventing signature forgery with an empty key. As a workaround, configure the `patreon_webhook_secret` site setting with a strong, non-empty secret value. When the secret is non-empty, an attacker cannot forge valid signatures without knowing the secret.

The advisory is available at github.com. This vulnerability is traded as CVE-2026-26078 since 02/10/2026. The exploitability is told to be easy. It is possible to launch the attack remotely. The exploitation doesn't require any form of authentication. The technical details are unknown and an exploit is not available.

Upgrading to version 2025.12.2, 2026.1.1 or 2026.2.0 eliminates this vulnerability.

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Productinfo

Type

• Chat Software

Name

• Discourse

Version

• 2025.12.0
• 2025.12.1
• 2026.0
• 2026.1.0

License

• open-source

Website

• Product: https://github.com/discourse/discourse/

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