Discourse ActivityPub: Fix inbound actor validation and apply outbound request SSRF hardening
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.
CVE-2026-55103
Primary source · Revision 1
Imported from structured advisory data. Source references identify upstream records or fields; verify affected versions and your deployed configuration.
Security context
Source reference: cve:CVE-2026-55103
discourse-activity-pub
Source reference: /containers/cna/affected/0/product
- Affected versions
- Not stated in this record
- Fixed versions
- Not stated in this record
- Prerequisites
- Not stated in this record
Structured affected-version data
Original package identities and version rules from this source.
[
{
"vendor": "discourse",
"product": "discourse-activity-pub",
"versions": [
{
"status": "affected",
"version": "< 1c8518b0f2abdf31cbea3e0b242f74d8994a9ba5"
}
]
}
]- Related CVEs
- CVE-2026-55103
Source reference:
/cveMetadata/cveId
Publisher severity
high
Source reference: /containers/cna/metrics
- Event
- #29875 · Revision 1
- Added to Heist Feed
- Publisher date