CVE-2026-55166

CRITICALPre-NVD 9.99.9—
EchelonGraph scoreMEDIUM confidence

This critical-severity CVE scores 9.9 under a secondary CVSS source (NVD's own analysis pending). EPSS exploit probability: 0.2%, top 88% of all CVEs by exploit prediction. GitHub Security Advisory data not yet ingested — confidence will rise once GHSA publishes (typical lag: hours to days for open-source ecosystem CVEs; never for infrastructure-only CVEs).

Triggered by: NVD CVSS baseline
Sources: epss, secondary
Elevated
9.9EG
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS PROB: 0%CVSS: 9.9Exploit: Elevated riskExposed: 0

No vendor fix yet — apply a workaround or compensating control (WAF / firewall / segmentation) and watch for a patch.

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.

CVSS v3
9.9
EG Score
9.9(medium)
EG Risk
61(Track*)
EG Risk 61/100SSVC: Track*

EG Risk is EchelonGraph's 0–100 priority score: it fuses intrinsic severity with real-world exploitation and automatability so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner. Distinct from the 0–10 EG Score (severity).

How it’s computed
Severity99% × 45%
Exploitation40% × 40%
Automatability0% × 15%
Action: Watch closely — could escalate to Attend.
EPSS PROB
0%
EPSS %ILE
12%
KEV
Not listed

Published

June 25, 2026

Last Modified

August 18, 2026

Advisory Details (3)

Auto-updated Aug 25, 2026
🔬 Proof of concept available. Patch available. Sources: github_commit, github_release, github.
github Patch Available🟡 PoC Available

Lemur 1.9.0: any SSO-authenticated user achieves AWS IAM compromise and permanent PKI key access via ACME acme_url SSRF and creator-equality IDOR · Advisory · Netflix/lemur · GitHub

https://github.com/Netflix/lemur/security/advisories/GHSA-v2wp-frmc-5q3v
github_release Patch Available

v1.9.2

Patch available: Netflix/lemur v1.9.2

https://github.com/Netflix/lemur/releases/tag/v1.9.2
github_commit Patch Available

commit 872f6e282542 (Netflix/lemur)

Patch available: Netflix/lemur v1.9.2 (contains commit 872f6e282542)

https://github.com/Netflix/lemur/commit/872f6e282542352f2bf3f6e2bcc504ab81e1843d

Vendor Advisories for CVE-2026-55166(1)

These vendors published their own advisory mentioning this CVE — often with vendor-specific remediation steps + affected product lists not in NVD.

Affected Packages

(1 across 1 ecosystem)
PyPI(1)
PackageVulnerable rangeFixed inDependents
lemur0.11.0 ... 1.9.1 (19 versions)1.9.2—

Weakness Classification(3)

MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.

Data Freshness Timeline

(refreshed 11× in last 7d / 17× in last 30d)

Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. Most recent first.

  1. 2026-08-26 14:46 UTCEPSS rescore
  2. 2026-08-25 13:49 UTCEPSS rescore
  3. 2026-08-24 21:50 UTCEG score recompute
  4. 2026-08-24 13:08 UTCEG score recompute
  5. 2026-08-23 02:25 UTCEG score recompute
  6. 2026-08-23 00:19 UTCEPSS rescore
  7. 2026-08-22 01:28 UTCEG score recompute
  8. 2026-08-21 23:49 UTCEPSS rescore
  9. 2026-08-20 23:59 UTCEG score recompute
  10. 2026-08-20 22:55 UTCEPSS rescore
  11. 2026-08-20 07:01 UTCEG score recompute
  12. 2026-08-19 17:04 UTCEPSS rescore
  13. 2026-08-19 01:13 UTCEG score recompute
  14. 2026-08-18 20:25 UTCEG score recompute
  15. 2026-08-18 19:45 UTCEG score recompute
  16. 2026-08-18 19:25 UTCEG score recompute
  17. 2026-07-30 13:58 UTCEG score recompute
  18. 2026-07-26 14:54 UTCEG score recompute
  19. 2026-07-23 03:20 UTCEG score recompute
  20. 2026-06-25 22:46 UTCEG score recompute

Related CVEs(same CWE)

Frequently asked(5)

What is CVE-2026-55166?
CVE-2026-55166 is a critical vulnerability published on June 25, 2026. Lemur manages TLS certificate creation. Prior to 1.9.2, authenticated users could influence an ACME authority acmeurl without an effective server-side destination restriction and trigger AcmeHandler.setupacmeclient to make backend requests. An attacker could target cloud instance metadata or…
When was CVE-2026-55166 disclosed?
CVE-2026-55166 was first published in the National Vulnerability Database on June 25, 2026, with the most recent update on August 18, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-55166 actively exploited?
CVE-2026-55166 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0% probability of exploitation in the next 30 days, which ranks it in the top 88.0% of all scored CVEs.
What is the CVSS score of CVE-2026-55166?
CVE-2026-55166 has a CVSS v3 base score of 9.9 (NVD).
How do I remediate CVE-2026-55166?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-55166, EchelonGraph cross-links them in the Vendor Advisories panel below — those typically contain the canonical remediation steps, fixed version numbers, and any vendor-specific mitigations.

Dependency Blast Radius

See which npm, PyPI, Go, and Maven packages are affected by CVE-2026-55166

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