CVE-2026-55103
8.6
Vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:N/A:N
Exploitability: 3.9 / Impact: 4.0
Source: security-advisories@github.com (Secondary)
Description
Discourse ActivityPub adds ActivityPub support to Discourse. Prior to commit 1c8518b0f2abdf31cbea3e0b242f74d8994a9ba5, inbound ActivityPub processing does not sufficiently verify that the actor authenticated by the signed request matches the Activity actor and owns the referenced federated post. A remote attacker can exploit these missing identity and ownership checks to edit, delete, or reply to federated posts without the required permissions. This vulnerability is fixed with commit 1c8518b0f2abdf31cbea3e0b242f74d8994a9ba5.
Related CWEs
CWE-345
Insufficient Verification of Data Authenticity
The product does not sufficiently verify the origin or authenticity of data, in a way that causes it to accept invalid data.
CWE-863
Incorrect Authorization
The product performs an authorization check when an actor attempts to access a resource or perform an action, but it does not correctly perform the check. This allows attackers to bypass intended access restrictions.
References (2)
Source: security-advisories@github.com
Source: security-advisories@github.com
Timeline
No history available yet.