CVE-2026-25808
Unauthorized Data Exposure in Hollo ActivityPub Outbox Endpoint
Publication date: 2026-02-09
Last updated on: 2026-02-28
Assigner: GitHub, Inc.
Description
Description
CVSS Scores
EPSS Scores
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Meta Information
Affected Vendors & Products
| Vendor | Product | Version / Range |
|---|---|---|
| fedify | hollo | From 0.6.0 (inc) to 0.6.20 (exc) |
| fedify | hollo | From 0.7.0 (inc) to 0.7.2 (exc) |
Helpful Resources
Exploitability
| CWE ID | Description |
|---|---|
| CWE-862 | The product does not perform an authorization check when an actor attempts to access a resource or perform an action. |
Attack-Flow Graph
AI Powered Q&A
Can you explain this vulnerability to me?
The vulnerability exists in Hollo, a federated single-user microblogging software using ActivityPub. Before versions 0.6.20 and 0.7.2, direct messages (DMs) and followers-only posts could be accessed through the ActivityPub outbox endpoint without proper authorization.
This means that private communications and restricted posts were exposed to unauthorized users.
The issue was fixed in versions 0.6.20 and 0.7.2.
How can this vulnerability impact me? :
This vulnerability can lead to unauthorized disclosure of private information, such as direct messages and posts intended only for followers.
Because the vulnerability allows exposure without authorization, sensitive or confidential communications could be accessed by unintended parties.
The CVSS base score of 7.5 indicates a high severity impact on confidentiality, though integrity and availability are not affected.
How does this vulnerability affect compliance with common standards and regulations (like GDPR, HIPAA)?:
I don't know
How can this vulnerability be detected on my network or system? Can you suggest some commands?
I don't know
What immediate steps should I take to mitigate this vulnerability?
To mitigate this vulnerability, you should upgrade Hollo to version 0.6.20 or 0.7.2 or later, as these versions contain the fix that prevents unauthorized exposure of DMs and followers-only posts through the ActivityPub outbox endpoint.