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CVE-2026-42180

6.3 · MEDIUM

Lemmy is a link aggregator and forum for the fediverse.

Published May 8, 2026CWE-918EPSS 0.29%

Overview

CVE-2026-42180 is a medium-severity vulnerability. It was published on May 8, 2026 and has a CVSS 3.1 base score of 6.3 (MEDIUM).

This vulnerability has a CVSS 3.1 base score of 6.3, rated MEDIUM. It can be exploited remotely over the network. Some level of privileges is required for exploitation.

Technical description

Lemmy is a link aggregator and forum for the fediverse. Prior to version 0.19.18, Lemmy allows an authenticated low-privileged user to create a link post through POST /api/v3/post. When a post is created in a public community, the backend asynchronously sends a Webmention to the attacker-controlled link target. The submitted URL is checked for syntax and scheme, but the audited code path does not reject loopback, private, or link-local destinations before the Webmention request is issued. This lets a normal user trigger server-side HTTP requests toward internal services. This issue has been patched in version 0.19.18.

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/LemmyNet/lemmy/releases/tag/0.19.18GitHubgithub.com/LemmyNet/lemmy/security/advisories/GHSA-3jvj-v6w2-h948GitHubgithub.com/LemmyNet/lemmy/security/advisories/GHSA-3jvj-v6w2-h948

How CyberStrike helps

Frequently asked questions

What is CVE-2026-42180?

CVE-2026-42180 is a medium-severity vulnerability. It was published on May 8, 2026 and has a CVSS 3.1 base score of 6.3 (MEDIUM).

How severe is CVE-2026-42180?

This vulnerability has a CVSS 3.1 base score of 6.3, rated MEDIUM. It can be exploited remotely over the network. Some level of privileges is required for exploitation.

How do I fix or remediate CVE-2026-42180?

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-2026-42180?

CyberStrike is an open-source, AI-augmented pentesting engine. Rather than flag a version number, it tests whether an issue like CVE-2026-42180 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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