CVE-2026-25808
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Unauthorized Data Exposure in Hollo ActivityPub Outbox Endpoint

Publication date: 2026-02-09

Last updated on: 2026-02-28

Assigner: GitHub, Inc.

Description
Hollo is a federated single-user microblogging software designed to be federated through ActivityPub. Prior to 0.6.20 and 0.7.2, there is a security vulnerability where DMs and followers-only posts were exposed through the ActivityPub outbox endpoint without authorization. This vulnerability is fixed in 0.6.20 and 0.7.2.
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Meta Information
Published
2026-02-09
Last Modified
2026-02-28
Generated
2026-06-16
AI Q&A
2026-02-10
EPSS Evaluated
2026-06-15
NVD
CVE-2026-25808
Affected Vendors & Products
Showing 2 associated CPEs
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
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KEV
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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.
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Executive Summary

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.

Impact Analysis

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.

Compliance Impact

I don't know

Detection Guidance

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Mitigation Strategies

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.

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