CVE-2026-47389

Mastodon is a free, open-source social network server based on ActivityPub. Prior to 4.5.10, 4.4.17, and 4.3.23, when using Ruby versions older than 3.4, PrivateAddressCheck.private_address? returns false for IPv4-mapped IPv6 addresses (::ffff:a.b.c.d) corresponding to some private IPv4 addresses, depending on Ruby version, this can include loopback, RFC1918 private networks, and link-local space. An attacker who controls DNS for any domain can publish an AAAA record with such a mapped address; any outbound HTTP fetch Mastodon performs against that hostname then opens a real TCP connection to the underlying IPv4 address, including 127.0.0.1 and cloud-metadata endpoints such as 169.254.169.254. This vulnerability is fixed in 4.5.10, 4.4.17, and 4.3.23.

CVSS v3 8.6 HIGH

8.6^/10

CVSS v3 : HIGH

Vector :

Exploitability : 3.9 / Impact : 4.0

Attack Vector NETWORK

Attack Complexity LOW

Privileges Required NONE

User Interaction NONE

Confidentiality Impact HIGH

Integrity Impact NONE

Availability Impact NONE

Scope CHANGED

References

Link	Resource
https://github.com/mastodon/mastodon/security/advisories/GHSA-xx55-4rrg-8xg6

Configurations

No configuration.

History

24 Jun 2026, 20:16

Type	Values Removed	Values Added
New CVE

Information

Published : 2026-06-24 20:16

Updated : 2026-06-25 17:16

NVD link : CVE-2026-47389

Mitre link : CVE-2026-47389

CVE.ORG link : CVE-2026-47389

JSON object : View

Products Affected

No product.

CWE

CWE-184

Incomplete List of Disallowed Inputs

CWE-200

Exposure of Sensitive Information to an Unauthorized Actor

CWE-918

Server-Side Request Forgery (SSRF)

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