CVE-2026-72916Mastodon: SSRF Protection Bypass via IPv4-compatible IPv6 Addresses
Updated under an hour ago ()
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No exploitation reported and no EPSS estimate yet.
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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.
- CVSS
- 6.3 MEDIUM (v4.0, CNA)CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:N/VI:N/VA:N/SC:L/SI:L/SA:L
- Weakness (CWE)
- CWE-918, CWE-1286
- Known exploited
- Not in CISA's KEV catalog
- EPSS (exploitation in the next 30 days)
- Not loaded for this CVE
- Assigned by
- GitHub_M
- NVD analysis
- Deferred
- Record last updated
- Aug 13, 2026
- First seen by InfoSec Signals
- Oct 9, 2026
Affected products
mastodon mastodon mastodon:mastodon (from the name) | before 4.4.21; from 4.5.0-beta.1, < 4.5.14; from 4.6.0-beta.1, < 4.6.4 | CNA record |
References
- https://github.com/mastodon/mastodon/security/advisories/GHSA-vwhj-3g83-v276x-refsource-confirm
- https://github.com/mastodon/mastodon/commit/18c61f286f1f5718a8f517940ba384866ffa3892x-refsource-misc
- https://github.com/mastodon/mastodon/commit/467c933459c7d0e5513475b9e4888afaedfb1074x-refsource-misc
- https://github.com/mastodon/mastodon/commit/930aa9fee26bf9eaefe27826fa1061288d83373bx-refsource-misc
- https://github.com/mastodon/mastodon/commit/da47a1bd3cd07935d7ca55a1f4f1a76f7f167e0dx-refsource-misc
- https://github.com/mastodon/mastodon/releases/tag/v4.4.21x-refsource-misc
- https://github.com/mastodon/mastodon/releases/tag/v4.5.14x-refsource-misc
- https://github.com/mastodon/mastodon/releases/tag/v4.6.4x-refsource-misc
- https://github.com/mastodon/mastodon/releases/tag/v4.7.0-beta.1x-refsource-misc
The CVE record on cve.org NVD's entry
The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.