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Vulnerability record · CVE-2026-71303 · published 18 August 2026

CVE-2026-71303: Server-side request forgery (SSRF) vulnerability

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.

7.7 CVSS 3.1 High EPSS 0.28% · top 81.9% CWE-918 · Server-side request forgery (SSRF) Deferred
7.7CVSS 3.1 base score
0.28%EPSS exploitation probability, 30 days
NoNot in CISA KEV
0Affected product versions listed by NVD
4References
8 Sep 2026Last modified by NVD

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.

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

References

LinkTags
https://github.com/Netflix/lemur/commit/edca0390f930344d65ff4ca37a669c2320e3dfad
https://github.com/Netflix/lemur/releases/tag/v1.9.3
https://github.com/Netflix/lemur/security/advisories/GHSA-v5rc-cpwc-cfpr
https://github.com/Netflix/lemur/security/advisories/GHSA-v5rc-cpwc-cfpr

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Source: NIST National Vulnerability Database (record CVE-2026-71303), CISA KEV, FIRST EPSS (scores of 2026-09-27). This page is refreshed as NVD updates the record.