CVE-2026-72916 | Mastodon is a free, open-source social network server based on ActivityPub. Prior to 4.4.21, 4.5.14, 4.6.4, and 4.7.0-beta.1, PrivateAddressCheck.private_address? in app/lib/private_address_check.rb normalized IPv4-mapped IPv6 addresses but did not recognize IPv4-compatible IPv6 addresses with IPAddr#ipv4_compat?. An attacker could supply an address in the omitted range to bypass the ALLOWED_PRIVATE_ADDRESSES protection and make Mastodon send HTTP requests to
Mastodon is a free, open-source social network server based on ActivityPub. Prior to 4.4.21, 4.5.14, 4.6.4, and 4.7.0-beta.1, PrivateAddressCheck.private_address? in app/lib/private_address_check.rb normalized IPv4-mapped IPv6 addresses but did not recognize IPv4-compatible IPv6 addresses with IPAddr#ipv4_compat?. An attacker could supply an address in the omitted range to bypass the ALLOWED_PRIVATE_ADDRESSES protection and make Mastodon send HTTP requests to loopback interfaces, potentially accessing private resources and services. Exploitation requires a system that supports the obsolete IPv4-compatible IPv6 mechanism. This issue is fixed in versions 4.4.21, 4.5.14, 4.6.4, and 4.7.0-beta.1.
- 🔗 github.com/mastodon/mastodon/security/advisories/GHS…
- 🔗 github.com/mastodon/mastodon/commit/18c61f286f1f5718…
- 🔗 github.com/mastodon/mastodon/commit/467c933459c7d0e5…
- 🔗 github.com/mastodon/mastodon/commit/930aa9fee26bf9ea…
- 🔗 github.com/mastodon/mastodon/commit/da47a1bd3cd07935…
- 🔗 github.com/mastodon/mastodon/releases/tag/v4.4.21
- 🔗 github.com/mastodon/mastodon/releases/tag/v4.5.14
- 🔗 github.com/mastodon/mastodon/releases/tag/v4.6.4
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📊 Historien-Charts — Criticals-Trend · Vendors · EPSS-Verteilung
| Tier | 2026-08-29 | 2026-09-13 |
|---|---|---|
| ≥90 % | 4 | 0 |
| ≥50 % | 4 | 0 |
| ≥10 % | 3 | 0 |
| <10 % | 304 | 300 |
CVE-2026-72916 | Mastodon is a free, open-source social network server based on ActivityPub. Prior to 4.4.21, 4.5.14, 4.6.4, and 4.7.0-beta.1, PrivateAddressCheck.private_address? in app/lib/private_address_check.rb normalized IPv4-mapped IPv6 addresses but did not recognize IPv4-compatible IPv6 addresses with IPAddr#ipv4_compat?. An attacker could supply an address in the omitted range to bypass the ALLOWED_PRIVATE_ADDRESSES protection and make Mastodon send HTTP requests to
Mastodon is a free, open-source social network server based on ActivityPub. Prior to 4.4.21, 4.5.14, 4.6.4, and 4.7.0-beta.1, PrivateAddressCheck.private_address? in app/lib/private_address_check.rb normalized IPv4-mapped IPv6 addresses but