Security readout for executives and security teams
Plain-English summary
An authenticated Lemur user could make the certificate-management server contact normally unreachable systems, potentially exposing cloud credentials. A related authorization flaw could let certificate creators retain access to private keys after roles or ownership changed. Compromise could affect cloud resources and long-lived TLS identity. Netflix fixed both issues in Lemur 1.9.2.
Executive priority
If Lemur is deployed, identify its version immediately and prioritize upgrading any instance below 1.9.2. Treat exposed cloud credentials or private keys as potential incident-response scope, especially where many SSO users have access or Lemur holds valuable IAM permissions. If Lemur is absent or already upgraded, document that result.
Technical view
Before 1.9.2, Lemur did not effectively restrict the destination supplied through an ACME authority’s acme_url. AcmeHandler.setup_acme_client could therefore request cloud metadata or internal services. Separate creator-equality authorization could preserve private-key access after ownership or role changes, while export_private_key auditing lacked distinguishing context. Version 1.9.2 adds host allowlisting and richer audit context.
Likely exposure
Exposure is limited to Netflix Lemur versions earlier than 1.9.2. Risk is highest where SSO-authenticated users can influence ACME authorities, Lemur can reach cloud metadata or sensitive internal services, and creators’ access should end after ownership or role changes. The bundle provides no CPEs or deployment-prevalence data.
Exploitation context
The CVE is not listed in KEV, and the supplied sources do not report active exploitation or a public exploit. Abuse requires an authenticated user but no user interaction; the CVSS vector rates attack complexity and required privileges as low. Actual impact depends on reachable services, host credentials, and available certificate key material.
Researcher notes
Key validation points are destination enforcement before AcmeHandler.setup_acme_client, creator-versus-current-owner authorization after lifecycle changes, and whether enriched export_private_key events support reliable attribution. The sources describe potential AWS IAM compromise but do not establish which credentials were reachable in any specific deployment or confirm exploitation.
Mitigation direction
- Upgrade Netflix Lemur to version 1.9.2 or later, following the vendor release and advisory.
- Configure and verify ACME_DIRECTORY_HOST_ALLOWLIST so only approved ACME directory hosts are accepted.
- Restrict Lemur access to trusted users until upgrading and validation are complete.
- Investigate and rotate potentially exposed cloud credentials and PKI private keys when evidence indicates unauthorized access.
Validation and detection
- Inventory Lemur deployments and confirm no running version is earlier than 1.9.2.
- Review ACME authority records for unexpected acme_url destinations, especially metadata or internal-service addresses.
- Verify server-side allowlisting rejects all unapproved ACME directory hosts.
- Review key-export audits alongside creator, current-owner, role-change, and ownership-change history.
- Correlate Lemur outbound requests with cloud IAM activity and unusual credential use.
Public sources used
Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.
Conservative CVE-to-ATT&CK context
These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.
ATT&CK lookup starting points
Use these exact CWE pages and searches to review the Glexia ATT&CK library from this CVE's weakness and description context.
CWE-285: Exact CWE lookup
Use the exact CWE identifier as the starting point before reviewing related ATT&CK behavior. Open the exact CWE lookup page first, then review the ATT&CK searches from that MITRE weakness context. This is a Glexia lookup hint, not an official ATT&CK mapping.
Open ATT&CK lookupCWE-639: Exact CWE lookup
Use the exact CWE identifier as the starting point before reviewing related ATT&CK behavior. Open the exact CWE lookup page first, then review the ATT&CK searches from that MITRE weakness context. This is a Glexia lookup hint, not an official ATT&CK mapping.
Open ATT&CK lookupCWE-918: Information exposure and cloud metadata lookup
Information exposure and SSRF weaknesses can make discovery, cloud metadata, and credential material review relevant. Open the exact CWE lookup page first, then review the ATT&CK searches from that MITRE weakness context. This is a Glexia lookup hint, not an official ATT&CK mapping.
Open ATT&CK lookupCloud metadata behavior lookup
The CVE wording references SSRF or metadata access, so cloud discovery and credential material review may help. This is a Glexia inferred lookup path, not an official MITRE, ATT&CK, or CVE Program mapping.
Open ATT&CK lookupCVE-2026-55166 mapping review
Open the CVE-to-ATT&CK bridge for reviewed, inferred, or future official mappings tied to this CVE.
Open ATT&CK lookup- Severity
- Critical
- CVSS
- 9.9 (3.1)
- Known Exploited
- No
- Published
Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:L
CNA and ADP enrichment extracted from CVE v5
These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.
SSVC decision data
CVSS vector scores
1 official scoreWe collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:L3.16GitHub_MVulnerability scoring details
Base CVSS 3.1 score
9.9CriticalVector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:L
Vulnerability timeline
Timeline events are normalized from CVE metadata, CNA source timelines, ADP timelines, and KEV metadata when present.
- CVE reservedCVE Program
The CVE ID was reserved by the assigning CNA.
- CVE publishedCVE Program
The CVE record was published.
- CVE updatedCVE Program
The CVE record metadata indicates this as the latest update time.
ADP provider summaries
Source materials
- CVE List V5 sourceCVE List V5
- https://github.com/Netflix/lemur/security/advisories/GHSA-v2wp-frmc-5q3vCVE reference, GitHub_M · x_refsource_CONFIRM
- https://github.com/Netflix/lemur/commit/872f6e282542352f2bf3f6e2bcc504ab81e1843dCVE reference, GitHub_M · x_refsource_MISC
- https://github.com/Netflix/lemur/releases/tag/v1.9.2CVE reference, GitHub_M · x_refsource_MISC
Products and packages named in the record
CWE details
CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.
Improper Authorization
Improper Authorization represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.
Authorization Bypass Through User-Controlled Key
Authorization Bypass Through User-Controlled Key represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.
Server-Side Request Forgery
Server-Side Request Forgery represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.