---
id: CVE-2026-55166
title: Lemur manages TLS certificate creation
summary: >-
  Lemur manages TLS certificate creation. Prior to 1.9.2, authenticated users
  could influence an ACME authority acme_url without an effective server-side
  destination restriction and trigger AcmeHandler.setup_acme_client to make
  backend req…
severity: critical
cvss: 9.9
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:L'
cwe:
  - CWE-285
  - CWE-639
  - CWE-918
vendor: lemur
product: lemur
affected:
  - lemur < 1.9.2
patched:
  - lemur 1.9.2
published: '2026-08-18'
updated: '2026-09-08'
sourceUpdated: '2026-09-08T21:02:26.047'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-55166'
references:
  - url: >-
      https://github.com/Netflix/lemur/commit/872f6e282542352f2bf3f6e2bcc504ab81e1843d
    label: security-advisories@github.com
  - url: 'https://github.com/Netflix/lemur/releases/tag/v1.9.2'
    label: security-advisories@github.com
  - url: 'https://github.com/Netflix/lemur/security/advisories/GHSA-v2wp-frmc-5q3v'
    label: security-advisories@github.com
  - url: 'https://github.com/Netflix/lemur/security/advisories/GHSA-v2wp-frmc-5q3v'
    label: 134c704f-9b21-4f2e-91b3-4a467353bcc0
  - url: 'https://github.com/advisories/GHSA-v2wp-frmc-5q3v'
tags:
  - nvd
  - ghsa
  - pip
epss: 0.00276
epssPercentile: 0.20225
ecosystem: pip
ingestedAt: '2026-06-26T16:43:14.202Z'
---

## Overview

Lemur manages TLS certificate creation. Prior to 1.9.2, authenticated users could influence an ACME authority acme_url without an effective server-side destination restriction and trigger AcmeHandler.setup_acme_client to make backend requests. An attacker could target cloud instance metadata or internal services from Lemur network context, potentially obtaining credentials available to the host. The advisory also identifies creator-equality authorization behavior that could preserve access to certificate key material after ownership or role changes, with insufficient export_private_key audit context to distinguish that access path. Together, the acme_url server-side request forgery and authorization weakness could expose cloud credentials and long-lived PKI private-key access. The fix adds ACME_DIRECTORY_HOST_ALLOWLIST validation and enriches key-export audit events with creator and current-owner context. This issue is fixed in version 1.9.2.

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.

## Package advisory (CVE-2026-55166)

Affected packages:

- `lemur < 1.9.2`

Patched in:

- `lemur 1.9.2`

Source: https://github.com/advisories/GHSA-v2wp-frmc-5q3v