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CVE-2026-71303— Lemur: Incomplete fix for CVE-2026-55166 -- ACME authority update endpoint allows non-admin to replace `acme_url` with internal IP, bypassing allowlist

Quick assessment

Affected
Netflix lemur
Exploitation
Public or AI PoC available; prioritize validation
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

Netflix lemur是美国Netflix公司开源的一个证书管理工具。 Netflix lemur 1.9.3之前版本存在服务端请求伪造漏洞，该漏洞源于对acme_url验证不足，PUT /api/1/authorities/接口传递选项时未应用ACME_DIRECTORY_HOST_ALLOWLIST检查，持有authority角色的用户可将存储的acme_url替换为内部服务或实例元数据URL，导致服务端请求伪造，可能暴露内部服务或云元数据。

CVSS 7.7 · High EPSS 0.21% · P12

Possible ATT&CK Techniques 1 AI

T1530 · Data from Cloud Storage

Affected Version Matrix 1

VendorProduct Version RangeStatus
Netflix lemur < 1.9.3 affected
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I. Basic Information for CVE-2026-71303

Vulnerability Information
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Vulnerability Title
Lemur: Incomplete fix for CVE-2026-55166 -- ACME authority update endpoint allows non-admin to replace `acme_url` with internal IP, bypassing allowlist
Source: CVE Program / CVE List V5
Vulnerability Description
Lemur manages TLS certificate creation. Prior to 1.9.3, _validate_acme_url enforced ACME_DIRECTORY_HOST_ALLOWLIST when an authority was created, but PUT /api/1/authorities/ passed options to lemur/authorities/service.py without applying the same check. A user holding an authority role could replace the stored acme_url with an internal service or instance-metadata URL such as 169.254.169.254. The next issuance operation loaded that value and passed it to ClientV2.get_directory, causing an outbound request from the Lemur backend. This bypassed the creation-time mitigation for CVE-2026-55166 and could expose internal services or cloud metadata. The fix revalidates acme_url whenever authority options are updated. This issue is fixed in version 1.9.3.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:N/A:N
Source: CVE Program / CVE List V5
Vulnerability Type
服务端请求伪造(SSRF)
Source: CVE Program / CVE List V5
Vulnerability Title
Netflix lemur 服务端请求伪造漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
Netflix lemur是美国Netflix公司开源的一个证书管理工具。 Netflix lemur 1.9.3之前版本存在服务端请求伪造漏洞，该漏洞源于对acme_url验证不足，PUT /api/1/authorities/接口传递选项时未应用ACME_DIRECTORY_HOST_ALLOWLIST检查，持有authority角色的用户可将存储的acme_url替换为内部服务或实例元数据URL，导致服务端请求伪造，可能暴露内部服务或云元数据。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
Netflix lemur < 1.9.3 -

II. Public POCs for CVE-2026-71303

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Qwen3.6-35B-A3B · 10274 chars
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III. Intelligence Information for CVE-2026-71303

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Patches & Fixes for CVE-2026-71303 (1)

Vendor Advisories for CVE-2026-71303 (1)

Vendor Pages for CVE-2026-71303 (1)

Same Patch Batch · Netflix · 2026-08-18 · 14 CVEs total

CVE-2026-55166 9.9 CRITICAL Lemur: any SSO-authenticated user achieves AWS IAM compromise and permanent PKI key access
CVE-2026-48508 8.8 HIGH Lemur: Authorization bypass in StrictRolePermission / AuthorityCreatorPermission
CVE-2026-71308 8.1 HIGH Lemur: Unchecked `replaces[]` lets any user silence notifications and hijack auto-rotation
CVE-2026-71307 7.7 HIGH Lemur: Authenticated low-privilege users can read plaintext destination credentials (SFTP
CVE-2026-70666 7.4 HIGH Lemur: Server-Side Request Forgery via the ACME client following server-controlled URLs
CVE-2026-71417 7.3 HIGH Lemur: Any user can revoke arbitrary certificates at the CA by uploading a duplicate recor
CVE-2026-71317 6.5 MEDIUM Lemur: Sub-CA creation never checks `AuthorityPermission` on the parent authority
CVE-2026-70667 6.3 MEDIUM Lemur: SSRF protection in certificate revocation checking bypassable via HTTP redirects an
CVE-2026-55162 6.3 MEDIUM Lemur: Post-authentication SSRF via certificate verification - attacker-controlled CRL and
CVE-2026-55163 6.3 MEDIUM Lemur: Privilege escalation via PUT /api/1/roles/<id> — non-admin role members can rewrite
CVE-2026-55164 4.9 MEDIUM Lemur: Plaintext password storage in Lemur user-update path
CVE-2026-55165 4.8 MEDIUM Lemur : JWT verifier trusts attacker-supplied alg from token header — defense-in-depth gap
CVE-2026-71322 4.3 MEDIUM Lemur: Missing authorization check on POST /certificates/<id>/export for plugins with requ

IV. Related Vulnerabilities

Same product: lemur
Same vendor: Netflix
Same weakness: CWE-918

V. Comments for CVE-2026-71303

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