CVE-2026-71303Public exploitNetwork attack vector

Internal data access via unchecked acme_url update

Published Aug 18, 2026 · Updated Aug 18, 2026

Server-side request forgery in Netflix Lemur before 1.9.3 allows remote authenticated users to read internal services via ACME authority updates. The PUT /api/1/authorities/ path stores attacker-supplied options in lemur/authorities/service.py without re-running validate_acme_url, so a modified acme_url bypasses the creation-time host allowlist and is later passed to ClientV2.get_directory. Exploitation requires membership in an authority role and a later certificate issuance through that authority, letting the backend reach instance-metadata or other internal HTTP endpoints.

CVSS severity7.7
High
EPSS probability0.27%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Server-side request forgery in Netflix Lemur before 1.9.3 allows remote authenticated users to read internal services via ACME authority updates. The PUT /api/1/authorities/ path stores attacker-supplied options in lemur/authorities/service.py without re-running validate_acme_url, so a modified acme_url bypasses the creation-time host allowlist and is later passed to ClientV2.get_directory. Exploitation requires membership in an authority role and a later certificate issuance through that authority, letting the backend reach instance-metadata or other internal HTTP endpoints.

The record

CVE
CVE-2026-71303
Published
Aug 18, 2026
Updated
Aug 18, 2026
Vendor
Netflix
Product
Lemur
Classifications
CWE-918, T1190
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Aug 18, 2026CVE publishedPublication date reported by the CVE source.
  2. Aug 18, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=< 1.9.3

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

Netflix · Lemurversion=< 1.9.3

Published CVSS scores

7.7NVDCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:N/A:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-918Server-Side Request Forgery (SSRF)
T1190Exploit Public-Facing Application

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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