---
title: "Discourse ActivityPub - Broken Access Control"
description: "Discourse ActivityPub prior to commit 1c8518b0f2abdf31cbea3e0b242f74d8994a9ba5 contains a broken access control vulnerability caused by insufficient verification of actor identity and ownership in inbound ActivityPub processing, letting remote attackers edit, delete, or reply to federated posts without permissions, exploit requires crafted signed requests."
url: https://panop.io/threat-heartbeat/CVE-2026-55103/
---

# CVE-2026-55103 Discourse ActivityPub - Broken Access Control

Discourse ActivityPub prior to commit 1c8518b0f2abdf31cbea3e0b242f74d8994a9ba5 contains a broken access control vulnerability caused by insufficient verification of actor identity and ownership in inbound ActivityPub processing, letting remote attackers edit, delete, or reply to federated posts without permissions, exploit requires crafted signed requests.

CVSS base score 8.6 /10

High

CISA KEV

Not listed

Public exploit

None known

Authentication

Not required

[View the NVD record ↗](https://nvd.nist.gov/vuln/detail/CVE-2026-55103)

## Details

Type

Broken Access Control

Impact

Data Tampering

CVSS vector

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:N/A:N

Published

15 October 2026

Updated

16 October 2026

Weakness

[CWE-345](https://cwe.mitre.org/data/definitions/345.html)

## Vendor fix

Update to the version including commit 1c8518b0f2abdf31cbea3e0b242f74d8994a9ba5 or later.

Patching closes this CVE. It does not tell you which of your systems run the affected version, or what else is exposed alongside them.

## References

- [https://nvd.nist.gov/vuln/detail/CVE-2026-55103](https://nvd.nist.gov/vuln/detail/CVE-2026-55103)
- [https://github.com/discourse/discourse-activity-pub/commit/1c8518b0f2abdf31cbea3e0b242f74d8994a9ba5](https://github.com/discourse/discourse-activity-pub/commit/1c8518b0f2abdf31cbea3e0b242f74d8994a9ba5)
- [https://github.com/discourse/discourse-activity-pub/security/advisories/GHSA-jw39-rch6-mhwf](https://github.com/discourse/discourse-activity-pub/security/advisories/GHSA-jw39-rch6-mhwf)

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## What this record can't tell you

- Whether you run the affected software, and where
- Whether an attacker can actually reach and exploit it
- The misconfigurations that never get a CVE number
- What it would cost the business, ranked into what to fix first

Panop answers these inside your environment, for this CVE and every other finding.

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