What’s Vulnerable › Vulnerabilities

CVE-2026-42181: Lemmy: SSRF and internal image disclosure in post link metadata via unvalidated og:image

• Severity: medium (CVSS 6.5 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.2% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-05-08 · updated 2026-10-26
• Weakness: CWE-918

Description

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.

Affected products

• LemmyNet lemmy: before 0.19.18

References

• https://github.com/LemmyNet/lemmy/releases/tag/0.19.18
• https://github.com/LemmyNet/lemmy/security/advisories/GHSA-h6hf-9846-xwrq
• https://github.com/LemmyNet/lemmy/security/advisories/GHSA-h6hf-9846-xwrq

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