CVE-2026-55103

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Source
https://cve.org/CVERecord?id=CVE-2026-55103
Import Source
https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-55103.json
JSON Data
https://api.osv.dev/v1/vulns/CVE-2026-55103
Aliases
  • GHSA-jw39-rch6-mhwf
Published
2026-10-15T17:05:41Z
Modified
2026-10-16T02:48:06Z
Severity
  • 8.6 (High) CVSS_V3 - CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:N/A:N CVSS Calculator
Summary
Discourse ActivityPub: Fix inbound actor validation and apply outbound request SSRF hardening
Details

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.

Database specific 
{
    "cna_assigner":  "GitHub_M",
    "cwe_ids":  [
        "CWE-345",
        "CWE-863"
    ],
    "osv_generated_from":  "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/55xxx/CVE-2026-55103.json"
}
References

Affected packages

Git / github.com/discourse/discourse-activity-pub

Affected ranges

Type
GIT
Repo
https://github.com/discourse/discourse-activity-pub
Events
Introduced
0 Unknown introduced commit / All previous commits are affected
Fixed
1c8518b0f2abdf31cbea3e0b242f74d8994a9ba5

Database specific

source 
"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-55103.json"