Discourse
CVE-2026-26078
HIGH
Attack ChainAIDerived
Hypothetical attack flow derived from CVE metadata – not a confirmed exploit chain
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AccessIdentify blank patreon_webhook_secret setting
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DeliveryCompute HMAC-MD5 with empty key
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ExploitForge valid webhook signature
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ExecutionSend arbitrary Patreon webhook payload
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ImpactModify pledge data and group synchronization
Vulnerability Assessment
| Weakness |
CWE
OWASP Top 10:2025
A01:2025 - Broken Access Control
ASVS 5.0
V8 - Authorization Object-level authorization, IDOR prevention
|
| Exploitation Conditions | patreon_webhook_secret site setting must be blank (unconfigured). No authentication required. Attacker needs knowledge of Discourse webhook endpoint URL and request body format. |
| Impact | CVSS 7.5 (HIGH). Attack vector: Network. Complexity: Low. Privileges required: None. User interaction: None. Exploitation no authentication required. |
| Exploit ScenarioDerived | An attacker without authentication could exploit this vulnerability to compromise the affected system. |
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Alert meAnalysisAIv1 – Mar 12, 2026
Discourse instances with an unconfigured patreon_webhook_secret allow remote attackers to forge valid webhook signatures using an empty HMAC-MD5 key, enabling arbitrary creation, modification, or deletion of Patreon pledge data and unauthorized patron synchronization. The vulnerability affects Discourse versions prior to 2025.12.2, 2026.1.1, and 2026.2.0, and currently lacks an available patch. Administrators must explicitly configure the patreon_webhook_secret setting or upgrade to patched versions to mitigate this integrity attack.
Earlier versions of this analysis (1)
Discourse versions up to 2025.12.2 is affected by authorization bypass through user-controlled key (CVSS 7.5).
RemediationAI
Monitor vendor advisories for a patch. Restrict network access to the affected service where possible.
Affects your stack
Find out whether the stacks and servers you run are on an affected version.
Checking this CVE against your own stacks and servers is part of the Basic plan and up.
Technical ContextAI · show details
This vulnerability (CWE-639: Authorization Bypass Through User-Controlled Key) affects Discourse. 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-
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- Exploit and PoC references, threat intelligence from 22 sources
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Severity by source
AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
Primary rating from GitHub Advisory · only source for this CVE.
CVSS VectorGitHub Advisory
DescriptionGitHub Advisory
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.
Executive ViewAI
Discourse instances with blank Patreon webhook secrets are vulnerable to forged webhook attacks, allowing attackers to manipulate pledge data and trigger unauthorized actions without a patch currently available. Organizations using Discourse with Patreon integration face risk of data integrity compromise and potential revenue or membership management disruptions.
Generate and configure a strong random value for patreon_webhook_secret setting (do not leave blank); disable or restrict access to Patreon webhook endpoints via Web Application Firewall; implement IP whitelisting to allow webhooks only from verified Patreon service IP addresses; increase logging and monitoring of webhook endpoint access and Patreon-related data modifications; consider temporarily disabling Patreon integration if not critical to operations until patch availability.
Threat Intelligence Overview
NVD
CVE.org
EPSS
GitHub
How this decision was reached
The engine reads each signal below and applies a fixed list of rules from top to bottom. The first rule that matches sets the recommended action – like a statement, every line is shown.
What every action level means
SSVC AssessmentENISA
Priority Score
Attack Technique
Authentication bypass attacks exploit flaws in the verification mechanisms that control access to systems and applications.
Affected Products (CPE)GitHub Advisory
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discourse-bbcode is the official BBCode plugin for Discourse. Rated critical severity (CVSS 9.8), this vulnerability is
Unauthorized information disclosure in Discourse discussion platform versions prior to 2026.3.0-latest.1, 2026.2.1, and
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Discourse versions prior to 2025.12.2, 2026.1.1, and 2026.2.0 contain an insecure direct object reference (IDOR) in the
In Discourse 2.7.0 through beta1, a rate-limit bypass leads to a bypass of the 2FA requirement for certain forms. Rated
Unauthenticated attackers can submit forged webhook payloads to multiple email provider integrations in Discourse versio
Discourse is an open-source discussion platform. Rated medium severity (CVSS 6.5), this vulnerability is remotely exploi
Discourse is an open source platform for community discussion. Rated medium severity (CVSS 5.9), this vulnerability is r
Discourse versions prior to 3.4.4 (stable), 3.5.0.beta5 (beta), and 3.5.0.beta6-dev (tests-passed) contain a critical vu
Discourse is an open source platform for community discussion. Rated critical severity (CVSS 9.8), this vulnerability is
Discourse Patreon enables syncronization between Discourse Groups and Patreon rewards. Rated critical severity (CVSS 9.8
Exploit-DB