CVE-2026-55166
Lemur: any SSO-authenticated user achieves AWS IAM compromise and permanent PKI key access via ACME acme_url SSRF and creator-equality IDOR
Description
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.
INFO
Published Date :
Aug. 18, 2026, 7:16 p.m.
Last Modified :
Aug. 18, 2026, 8:17 p.m.
Remotely Exploit :
Yes !
Source :
[email protected]
CVSS Scores
| Score | Version | Severity | Vector | Exploitability Score | Impact Score | Source |
|---|---|---|---|---|---|---|
| CVSS | 134c704f-9b21-4f2e-91b3-4a467353bcc0 | |||||
| CVSS 3.1 | CRITICAL | [email protected] |
Solution
- Update Lemur to version 1.9.2.
- Implement ACME_DIRECTORY_HOST_ALLOWLIST validation.
- Enrich key-export audit events.
References to Advisories, Solutions, and Tools
Here, you will find a curated list of external links that provide in-depth
information, practical solutions, and valuable tools related to
CVE-2026-55166.
CWE - Common Weakness Enumeration
While CVE identifies
specific instances of vulnerabilities, CWE categorizes the common flaws or
weaknesses that can lead to vulnerabilities. CVE-2026-55166 is
associated with the following CWEs:
Common Attack Pattern Enumeration and Classification (CAPEC)
Common Attack Pattern Enumeration and Classification
(CAPEC)
stores attack patterns, which are descriptions of the common attributes and
approaches employed by adversaries to exploit the CVE-2026-55166
weaknesses.
We scan GitHub repositories to detect new proof-of-concept exploits. Following list is a collection of public exploits and proof-of-concepts, which have been published on GitHub (sorted by the most recently updated).
Results are limited to the first 15 repositories due to potential performance issues.
The following list is the news that have been mention
CVE-2026-55166 vulnerability anywhere in the article.
The following table lists the changes that have been made to the
CVE-2026-55166 vulnerability over time.
Vulnerability history details can be useful for understanding the evolution of a vulnerability, and for identifying the most recent changes that may impact the vulnerability's severity, exploitability, or other characteristics.
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CVE Modified by 134c704f-9b21-4f2e-91b3-4a467353bcc0
Aug. 18, 2026
Action Type Old Value New Value Added Reference https://github.com/Netflix/lemur/security/advisories/GHSA-v2wp-frmc-5q3v Added SSVC {'id': 'CVE-2026-55166', 'role': 'CISA Coordinator', 'options': [{'exploitation': 'poc'}, {'automatable': 'no'}, {'technicalImpact': 'total'}], 'version': '2.0.3', 'timestamp': '2026-08-18T19:33:55.265998Z'} -
New CVE Received by [email protected]
Aug. 18, 2026
Action Type Old Value New Value Added Affected [{'vendor': 'Netflix', 'product': 'lemur', 'versions': [{'status': 'affected', 'version': '< 1.9.2'}]}] Added Description 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. Added CVSS V3.1 AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:L Added CWE CWE-285 Added CWE CWE-918 Added CWE CWE-639 Added Reference https://github.com/Netflix/lemur/commit/872f6e282542352f2bf3f6e2bcc504ab81e1843d Added Reference https://github.com/Netflix/lemur/releases/tag/v1.9.2 Added Reference https://github.com/Netflix/lemur/security/advisories/GHSA-v2wp-frmc-5q3v