Lemmy has unauthenticated SSRF via file_type query parameter injection in image endpoint

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS 4.0

7.7 · CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N/E:P · score source

EPSS

• CVE-2026-29178: 0.29% estimated exploitation activity in the next 30 days; percentile 21.54 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Summary The GET /api/v4/image/{filename} endpoint is vulnerable to unauthenticated SSRF through parameter injection in the filetype query parameter. An attacker can inject arbitrary query parameters into the internal request to pict-rs, including the proxy parameter which causes pict-rs to fetch arbitrary URLs. Affected code crates/routes/src/images/download.rs, lines 17-40 (getimage function): The filetype parameter (ImageGetParams.filetype: Option<String) is directly interpolated into the URL string without any validation or encoding. Since pict-rs's /image/process.{ext} endpoint supports a ?proxy={url} parameter for fetching remote images, an attacker can inject ?proxy=... via filetype to make pict-rs fetch arbitrary URLs. This endpoint does not require authentication (no LocalUserView extractor). PoC The response from the internal URL is streamed back to the attacker through pict-rs and Lemmy. Impact An unauthenticated attacker can: - Access cloud metadata services (AWS/GCP/Azure…

Published by the source

4 Mar 2026, 20:55 UTC

Last modified by the source

6 Mar 2026, 22:44 UTC

Source last checked

26 Oct 2026, 15:42 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-jvxv-2jjp-jxc3

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# Patch Next advisory brief: CVE-2026-29178

Advisory: Lemmy has unauthenticated SSRF via file_type query parameter injection in image endpoint
IDs: CVE-2026-29178, GHSA-jvxv-2jjp-jxc3
Record: https://patchnext.com/advisories/cve-2026-29178 (revision 1, source checked 26 Oct 2026, 15:42 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: High (CVSS 7.7)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: lemmy_routes 0.19.16. A vendor fix does not mean a deployment is fixed.

## Affected components
- crates.io lemmy_routes: affected <= 0.19.15; fixed in 0.19.16

## Suggested inspection (read-only)
- crates.io lemmy_routes: check the installed version with your package manager.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on lemmy_routes.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-jvxv-2jjp-jxc3 (GitHub-reviewed advisory GHSA-jvxv-2jjp-jxc3 lists affected ranges: crates.io lemmy_routes >=0 <=0.19.15)

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