SSRF in Lemmynet Lemmy

CVE-2026-42181

Lemmy is a link aggregator and forum for the fediverse. Prior to version 0.19.18, Lemmy fetches metadata for user-supplied post URLs and, under the default StoreLinkPreviews image mode, downloads the preview image through local pict-rs. While the top-level page URL is checked against internal IP ranges, the extracted og:image URL is not subject to the same restriction. As a result, an authenticated low-privileged user can submit an attacker-controlled public page whose Open Graph image points to an internal image endpoint. Lemmy will fetch that internal image server-side and store a local thumbnail that can then be served back to users. This issue has been patched in version 0.19.18.

Vulnerability class: SSRF (Server-Side Request Forgery)

Published · last modified .

CVSS v3 metric

CVSS v3 base score 6.5 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N.

EPSS exploit prediction

EPSS: 0.004 (26.6th percentile), scored .

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 27th percentile — 26.6% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS trend (30 days)EPSS over the last 30 days for CVE-2026-42181: held from 0.002 to 0.004.

EPSS over last 30 days · oldest: 0.002 · newest: 0.004 · change: +0.001

Affected products

Weakness classification (CWE)

References

Frequently asked questions

What is CVE-2026-42181?
CVE-2026-42181 is a medium-severity vulnerability in Lemmynet Lemmy, classified under Server-Side Request Forgery (SSRF). CVSS score: 6.5/10. Published 2026-05-08.
How severe is CVE-2026-42181?
Medium severity. CVSS v3 base score is 6.5 out of 10.