CVE-2026-22245 Details
Description
Mastodon is a free, open-source social network server based on ActivityPub. By nature, Mastodon performs a lot of outbound requests to user-provided domains. Mastodon, however, has some protection mechanism to disallow requests to local IP addresses (unless specified in `ALLOWED_PRIVATE_ADDRESSES`) to avoid the "confused deputy" problem. The list of disallowed IP address ranges was lacking some IP address ranges that can be used to reach local IP addresses. An attacker can use an IP address in the affected ranges to make Mastodon perform HTTP requests against loopback or local network hosts, potentially allowing access to otherwise private resources and services. This is fixed in Mastodon v4.5.4, v4.4.11, v4.3.17 and v4.2.29.
A vulnerability in Mastodon allows for server-side request forgery (SSRF) by bypassing protections against local IP address requests. Mastodon, which frequently makes outbound requests to user-specified domains, has safeguards to block requests to local IPs unless explicitly allowed. However, the list of disallowed IP ranges was incomplete, leaving some local addresses accessible. This flaw enables attackers to manipulate Mastodon into making HTTP requests to loopback or local network hosts, potentially exposing private resources and services.
Users can update to Mastodon versions 4.5.4, 4.4.11, 4.3.17, or 4.2.29 to address this vulnerability.
Metrics
CVSS 4.0 Severity and Vector Strings:
CVSS 3.x Severity and Vector Strings:
No data available for CVSS Version 2.0 on this CVE.
CISA-ADP
Assessed Jan 8, 2026References to Advisories, Solutions, and Tools
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Weakness Enumeration
| CWE-ID | CWE Name | Source |
|---|---|---|
| CWE-918 | Server-Side Request Forgery (SSRF) | [email protected] |
Affected Products
| Product | Versions |
|---|---|
| joinmastodon mastodon | < 4.2.29 >= 4.3.0, < 4.3.17 >= 4.4.0, < 4.4.11 >= 4.5.0, < 4.5.4 |
CPE
Remediation
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Change History
4 change records found show changes
| Date | Action | Recorded By |
|---|---|---|
| Jun 17, 2026 | CVE Modified | [email protected] |
| Jun 17, 2026 | CVE Modified | CISA-ADP |
| Jan 15, 2026 | Initial Analysis | [email protected] |
| Jan 8, 2026 | New CVE Received | [email protected] |