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Vulnerability · Published Jan 8, 2026 · Assigned by GitHub_M

CVE-2026-22245Mastodon has SSRF Protection bypass

High 7.1

In plain English

A high-severity server-side request forgery in mastodon from mastodon. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.3% (higher than 22% of all known vulnerabilities).

Severity (CVSS 4.0)7.1High
Exploit odds (30 days)0.3%top 78.4% of all CVEs
Exploited in the wildNo reportsCISA SSVC: none
Attack toolingNoneno public tooling known

Official 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.

Affected products (as reported)

VendorProductVersions
mastodon mastodon < 4.2.29>= 4.3.0-beta.1, < 4.3.17>= 4.4.0-beta.1, < 4.4.11>= 4.5.0-beta.1, < 4.5.4

Weakness: CWE-918 · Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N

References