CVE-2026-22245
HIGHCVSS Vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
Lifecycle Timeline
3Description
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.
Analysis
Mastodon's IP address filtering bypass (CWE-918) permits attackers to craft requests using unblocked IP ranges to reach local and loopback services, potentially exposing private resources and internal APIs. An unauthenticated remote attacker can exploit incomplete private address range validation in Mastodon instances to perform Server-Side Request Forgery (SSRF) attacks. …
Sign in for full analysis, threat intelligence, and remediation guidance.
Remediation
Within 7 days: Identify all affected systems and apply vendor patches promptly. Implement egress filtering and URL validation for server-side requests.
Sign in for detailed remediation steps.
Priority Score
Share
External POC / Exploit Code
Leaving vuln.today