Discourse ActivityPub: Fix inbound actor validation and apply outbound request SSRF hardening
Impact
Discourse ActivityPub is vulnerable due to insufficient verification of data authenticity and incorrect authorization. A remote attacker can exploit this to edit, delete, or reply to federated posts without required permissions. Affected versions are prior to commit 1c8518b0f2abdf31cbea3e0b242f74d8994a9ba5.
Summarized by @cf/meta/llama-3.3-70b-instruct-fp8-fast. Verify details against the original sources.Affected packages
Affected products
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discourse · GitHub_M
discourse-activity-pub
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discourse · GitHub_M
discourse-activity-pub
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affected
< 1c8518b0f2abdf31cbea3e0b242f74d8994a9ba5
Other versions: unknown
Original source 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.
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Evidence available
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Original records
CVE-2026-55103View the latest unmodified CVE JSON from the official source. It may be newer than this imported page.
cve.new JSON →Underlying weaknesses
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Contributing organizations · 2
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What changed
Follow changesLarge field values are marked as truncated previews. Original source snapshots remain retained.