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

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Summary

CVECVE-2026-71303
StatePUBLISHED
AssignerGitHub_M
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-08-18 20:17:23 UTC
Updated2026-08-18 20:17:23 UTC
DescriptionLemur 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.

Risk And Classification

Primary CVSS: v3.1 7.7 HIGH from [email protected]

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:N/A:N

Problem Types: CWE-918 | CWE-918 CWE-918: Server-Side Request Forgery (SSRF)

VersionSourceTypeScoreSeverityVector
3.1[email protected]Secondary7.7HIGHCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:N/A:N
3.1CNADECLARED7.7HIGHCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:N/A:N

CVSS v3.1 Breakdown

Attack Vector
Network
Attack Complexity
Low
Privileges Required
Low
User Interaction
None
Scope
Changed
Confidentiality
High
Integrity
None
Availability
None

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:N/A:N

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Netflix Lemur affected < 1.9.3 Not specified

References

ReferenceSourceLinkTags
github.com/Netflix/lemur/security/advisories/GHSA-v5rc-cpwc-cfpr 134c704f-9b21-4f2e-91b3-4a467353bcc0 github.com
github.com/Netflix/lemur/commit/edca0390f930344d65ff4ca37a669c2320e3dfad [email protected] github.com
github.com/Netflix/lemur/releases/tag/v1.9.3 [email protected] github.com
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