SSRF (Server-Side Request Forgery) in lemur (CVE-2026-70666)
Summary
SSRF in lemur (CVE-2026-70666). Risk of unauthorized operations or information disclosure. Exploitable via PUT /authorities/. Mitigation: upgrade to 1.9.3 or later.
Original description
The description as published by the source.
Summary
The 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/) 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.
Detail
Defect A - allowlist only at creation.
_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:
# lemur/authorities/views.py:417-424 (Authorities.put)
return service.update(
authority_id,
owner=data["owner"], description=data["description"],
active=data["active"], roles=data["roles"],
options=data.get("options") # <- acme_url lives here, NO re-validation
)
`Aut…
Source: GitHub Security Advisories (Global) NVD GitHub Advisory
Auto-generated summary
Assembled by SecPulse from the source data (CVSS, CWE, affected versions) using templates — no AI involved. Check the original description and references below for exact details.
A vulnerability tracked as CVE-2026-70666 has been found in lemur.
Attackers can target a specific entry point like PUT /authorities/ over the network to misuse the product.
Risk of unauthorized operations or information disclosure. CVSS score: 7.4/10.
What to do: upgrade lemur to 1.9.3 or later.
If unsure, ask your IT team or search "lemur CVE-2026-70666" on the vendor's site.
CVE-2026-70666 (lemur) — CWE-918 / CVSS v3 7.4
Attack vector: remote (network-reachable) / no user interaction
Attack surface: PUT /authorities/ / PUT /api/1/authorities/ / acme_url / options
Patched: 1.9.3 — apply immediately
Plan: 1) Audit SBOM/dependencies, 2) Stage→prod upgrade, 3) Add WAF/proxy monitoring on affected endpoints, 4) Hunt IOCs in logs.
Refs: see the GHSA / vendor advisory / patched release linked on this page.
SSRF (CWE-918) exists in lemur. Attackers reach the vulnerable code path via PUT /authorities/.
Check the vendor advisory for the affected versions of lemur. Attack surface: PUT /authorities/ / PUT /api/1/authorities/ / acme_url / options.
Severity: High (CVSS 7.4/10). Risk of unauthorized operations or information disclosure.
Update to 1.9.3.
Until the patch is applied: disable the affected feature, apply WAF rules, or restrict access via network ACLs.
Search webserver/proxy logs for unusual PUT /authorities/ requests with malformed payloads or SQL meta-characters. Run grep -r 'lemur' . against your dependency files (package-lock.json, requirements.txt, go.sum) to find affected services.
Response actions
Concrete steps and command examples for SOC/SRE teams to execute in order
-
1Identify exposure identify
grep -r 'lemur' . | grep -v node_modulesリポジトリと本番環境の依存ファイル (package-lock.json / requirements.txt / go.sum / Gemfile.lock 等) で
lemurを grep し、稼働しているサービス・バージョンを把握する。 -
2Hunt for indicators of compromise detect
grep 'PUT /authorities/' /var/log/nginx/access.log | grep -E '(unusual_payload|sqli_pattern)'アクセスログで
PUT /authorities/への異常なリクエスト (不正な認証ヘッダ・SQLメタ文字)を過去 30〜90日分捜索。WAF/SIEM があれば該当パスのアラート発火履歴を確認。 -
3Apply patch patch
Upgrade lemur to 1.9.3ステージング環境で 1.9.3 に上げて回帰テスト → 本番反映。回帰テストはアプリの主要ハッピーパスと、Step 2 で見つけた異常検知の続報チェックを含めること。
-
4Post-deployment verification verify
Replay attack against PUT /authorities/ on staging to confirm patch closes the vectorパッチ適用後、ステージングで PoC または同等の悪用パターンを再現して脆弱性が閉じたことを確認。本番では Step 2 と同じログクエリでアラート再発が無いか継続監視。
Affected packages
References
- advisory github.com
- advisory nvd.nist.gov
- package github.com
- package pypi.org
- web github.com
- web github.com
- web github.com