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CVE-2026-22245

7.5 · HIGH

Mastodon is a free, open-source social network server based on ActivityPub.

Published Jan 8, 2026CWE-918EPSS 0.29%

Overview

CVE-2026-22245 is a high-severity vulnerability. It was published on January 8, 2026 and has a CVSS 3.1 base score of 7.5 (HIGH).

This vulnerability has a CVSS 3.1 base score of 7.5, rated HIGH. It can be exploited remotely over the network. No authentication or special privileges are required for exploitation.

Technical 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.

Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

References

GitHubgithub.com/mastodon/mastodon/commit/0f4e8a6240b5af1f2c3f34d2793d8610c6ef2acaGitHubgithub.com/mastodon/mastodon/commit/17022907866710a72a1b1fc0a5ce9538bad1b4c3GitHubgithub.com/mastodon/mastodon/commit/71ae4cf2cf5138ccdda64b1b1d665849b688686dGitHubgithub.com/mastodon/mastodon/security/advisories/GHSA-xfrj-c749-jxxq

How CyberStrike helps

Frequently asked questions

What is CVE-2026-22245?

CVE-2026-22245 is a high-severity vulnerability. It was published on January 8, 2026 and has a CVSS 3.1 base score of 7.5 (HIGH).

How severe is CVE-2026-22245?

This vulnerability has a CVSS 3.1 base score of 7.5, rated HIGH. It can be exploited remotely over the network. No authentication or special privileges are required for exploitation.

How do I fix or remediate CVE-2026-22245?

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

How can CyberStrike help with CVE-2026-22245?

CyberStrike is an open-source, AI-augmented pentesting engine. Rather than flag a version number, it tests whether an issue like CVE-2026-22245 is actually reachable in your own applications and APIs, then verifies each finding before reporting it. That tells you if the weakness is a real, exploitable risk in your environment or a false positive you can safely deprioritize.

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