Mastodon: SSRF Protection Bypass via IPv4-compatible IPv6 Addresses
Summary
| CVE | CVE-2026-72916 |
|---|---|
| State | PUBLISHED |
| Assigner | GitHub_M |
| Source Priority | CVE Program / NVD first with legacy fallback |
| Published | 2026-08-10 22:17:10 UTC |
| Updated | 2026-08-10 22:17:10 UTC |
| Description | 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. |
Risk And Classification
Primary CVSS: v4.0 6.3 MEDIUM from [email protected]
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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
EPSS: 0.003590000 probability, percentile 0.287520000 (date 2026-08-11)
Problem Types: CWE-918 | CWE-1286 | CWE-918 CWE-918: Server-Side Request Forgery (SSRF) | CWE-1286 CWE-1286: Improper Validation of Syntactic Correctness of Input
| Version | Source | Type | Score | Severity | Vector |
|---|---|---|---|---|---|
| 4.0 | [email protected] | Secondary | 6.3 | MEDIUM | 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/E:X/C... |
| 4.0 | CNA | DECLARED | 6.3 | MEDIUM | 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 |
CVSS v4.0 Breakdown
Attack Vector
NetworkAttack Complexity
HighAttack Requirements
PresentPrivileges Required
NoneUser Interaction
NoneConfidentiality
NoneIntegrity
NoneAvailability
NoneSub Conf.
LowSub Integrity
LowSub Availability
LowCVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:N/VI:N/VA:N/SC:L/SI:L/SA:L/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
Vendor Declared Affected Products
References
| Reference | Source | Link | Tags |
|---|---|---|---|
| github.com/mastodon/mastodon/releases/tag/v4.5.14 | [email protected] | github.com | |
| github.com/mastodon/mastodon/commit/930aa9fee26bf9eaefe27826fa1061288d83... | [email protected] | github.com | |
| github.com/mastodon/mastodon/security/advisories/GHSA-vwhj-3g83-v276 | [email protected] | github.com | |
| github.com/mastodon/mastodon/commit/467c933459c7d0e5513475b9e4888afaedfb... | [email protected] | github.com | |
| github.com/mastodon/mastodon/commit/18c61f286f1f5718a8f517940ba384866ffa... | [email protected] | github.com | |
| github.com/mastodon/mastodon/releases/tag/v4.7.0-beta.1 | [email protected] | github.com | |
| github.com/mastodon/mastodon/commit/da47a1bd3cd07935d7ca55a1f4f1a76f7f16... | [email protected] | github.com | |
| github.com/mastodon/mastodon/releases/tag/v4.6.4 | [email protected] | github.com | |
| github.com/mastodon/mastodon/releases/tag/v4.4.21 | [email protected] | github.com | |
| CVE Program record | CVE.ORG | www.cve.org | canonical |
| NVD vulnerability detail | NVD | nvd.nist.gov | canonical, analysis |
No vendor comments have been submitted for this CVE.
There are currently no legacy QID mappings associated with this CVE.