Vulnerability in Mastodon Server Affects Private Address Checks
CVE-2026-47389

8.6HIGH

Key Information:

Vendor

Mastodon

Status
Mastodon
Vendor
CVE Published:
24 June 2026

What is CVE-2026-47389?

A vulnerability exists in Mastodon, an open-source social network server, where prior versions mishandle private IPv4 addresses due to issues in the PrivateAddressCheck.private_address? method. Using Ruby versions older than 3.4, this misconfiguration allows attackers with control over DNS to manipulate AAAA records. As a consequence, outbound HTTP fetches may unintentionally connect to sensitive IP addresses, such as local loopback or metadata endpoints, creating potential exposure of sensitive information. This issue is resolved in the latest updates: 4.5.10, 4.4.17, and 4.3.23.

Affected Version(s)

mastodon >= 4.5.0-beta.1, < 4.5.10

References

https://github.com/mastodon/mastodon/security/advisories/...
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CVSS V3.1

Score:
8.6
Severity:
HIGH
Confidentiality:
High
Integrity:
None
Availability:
High
Attack Vector:
Network
Attack Complexity:
Low
Privileges Required:
None
User Interaction:
None
Scope:
Changed

Timeline

  • Vulnerability published

  • Vulnerability Reserved

.