PT-2026-52079 · Mastodon · Mastodon
Published
2026-06-24
·
Updated
2026-06-24
·
CVE-2026-47389
CVSS v3.1
8.6
High
| Vector | AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:N/A:N |
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.
Fix
Incomplete List of Disallowed Inputs
SSRF
Information Disclosure
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Related Identifiers
Affected Products
Mastodon