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CVE-2026-71303

7.7 · HIGH

Lemur manages TLS certificate creation.

Published Aug 18, 2026CWE-918EPSS 0.28%

Overview

CVE-2026-71303 is a high-severity vulnerability. It was published on August 18, 2026 and has a CVSS 3.1 base score of 7.7 (HIGH).

This vulnerability has a CVSS 3.1 base score of 7.7, rated HIGH. It can be exploited remotely over the network. Some level of privileges is required for exploitation.

Technical description

Lemur manages TLS certificate creation. Prior to 1.9.3, _validate_acme_url enforced ACME_DIRECTORY_HOST_ALLOWLIST when an authority was created, but PUT /api/1/authorities/ passed options to lemur/authorities/service.py without applying the same check. A user holding an authority role could replace the stored acme_url with an internal service or instance-metadata URL such as 169.254.169.254. The next issuance operation loaded that value and passed it to ClientV2.get_directory, causing an outbound request from the Lemur backend. This bypassed the creation-time mitigation for CVE-2026-55166 and could expose internal services or cloud metadata. The fix revalidates acme_url whenever authority options are updated. This issue is fixed in version 1.9.3.

Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

References

GitHubgithub.com/Netflix/lemur/commit/edca0390f930344d65ff4ca37a669c2320e3dfadGitHubgithub.com/Netflix/lemur/releases/tag/v1.9.3GitHubgithub.com/Netflix/lemur/security/advisories/GHSA-v5rc-cpwc-cfprGitHubgithub.com/Netflix/lemur/security/advisories/GHSA-v5rc-cpwc-cfpr

How CyberStrike helps

Frequently asked questions

What is CVE-2026-71303?

CVE-2026-71303 is a high-severity vulnerability. It was published on August 18, 2026 and has a CVSS 3.1 base score of 7.7 (HIGH).

How severe is CVE-2026-71303?

This vulnerability has a CVSS 3.1 base score of 7.7, rated HIGH. It can be exploited remotely over the network. Some level of privileges is required for exploitation.

How do I fix or remediate CVE-2026-71303?

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

How can CyberStrike help with CVE-2026-71303?

CyberStrike is an open-source, AI-augmented pentesting engine. Rather than flag a version number, it tests whether an issue like CVE-2026-71303 is actually reachable in your own applications and APIs, then verifies each finding before reporting it. That tells you if the weakness is a real, exploitable risk in your environment or a false positive you can safely deprioritize.

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