Hollo
CVE-2026-25808
HIGH
Severity by source
AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
Primary rating from GitHub Advisory · only source for this CVE.
CVSS VectorGitHub Advisory
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
Lifecycle Timeline
4DescriptionGitHub Advisory
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.
AnalysisAI
Hollo versions prior to 0.6.20 and 0.7.2 improperly expose direct messages and followers-only posts through the ActivityPub outbox endpoint, allowing unauthenticated remote attackers to access sensitive user communications. Public exploit code exists for this authorization bypass vulnerability, enabling attackers to enumerate and retrieve private content intended for restricted audiences. …
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Attack ChainAIDerived
Hypothetical attack flow derived from CVE metadata
Vulnerability AssessmentAI
| Exploitation | Hollo instances running versions prior to 0.6.20 or 0.7.2 with ActivityPub federation enabled and accessible outbox endpoint. … Additional conditions and limiting factors are described in the full assessment. |
| Risk Assessment | CVSS 7.5 (HIGH). … Full risk analysis with EPSS, KEV, and SSVC signal comparison available after sign-in. |
| Exploit Scenario | An attacker without authentication could exploit this vulnerability to compromise the affected system. |
| Remediation | A vendor patch is available — apply it immediately. … Detailed patch versions, workarounds, and compensating controls in full report. |
Recommended ActionAI
Within 24 hours: Identify all Hollo instances in your environment and verify current versions. …
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External POC / Exploit Code
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