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CVE-2026-47389

Mastodon: SSRF protection bypass on older Ruby versions PUBLISHED

Description (CNA)

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.

Affected (CNA)

Vendor / productVersions
mastodon / mastodonaffected >= 4.5.0-beta.1, < 4.5.10

CWE

CWE-184, CWE-200, CWE-918

References

ADP enrichment

CISA-ADP

No English description supplied.

No references supplied.