Description
Lemur manages TLS certificate creation. Prior to 1.9.2, lemur/certificates/verify.py accepted CRL Distribution Point and OCSP responder URLs from uploaded certificate extensions and used them in crl_verify and ocsp_verify without adequate destination validation. An authenticated operator could submit a certificate through POST /api/1/certificates/upload and cause verify_string to reach loopback, RFC1918, link-local, or instance-metadata destinations such as 169.254.169.254. The requests could probe internal services and create side effects from the Lemur host network position. The CRL path also used an unbounded cache, allowing attacker-controlled entries to persist and consume memory. The fix validates destinations, supports explicit trusted-host allowlists, and bounds the CRL cache. This issue is fixed in version 1.9.2.
Published: 2026-08-18
Score: 6.3 Medium
EPSS: n/a
KEV: No
Impact: n/a
Action: n/a
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Remediation

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Tracking

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Advisories
Source ID Title
Github GHSA Github GHSA GHSA-54vg-pfh7-jq95 Lemur: Crafted CRL/OCSP URLs in uploaded certificates lead to post-authentication SSRF
History

Tue, 18 Aug 2026 19:00:00 +0000

Type Values Removed Values Added
Description Lemur manages TLS certificate creation. Prior to 1.9.2, lemur/certificates/verify.py accepted CRL Distribution Point and OCSP responder URLs from uploaded certificate extensions and used them in crl_verify and ocsp_verify without adequate destination validation. An authenticated operator could submit a certificate through POST /api/1/certificates/upload and cause verify_string to reach loopback, RFC1918, link-local, or instance-metadata destinations such as 169.254.169.254. The requests could probe internal services and create side effects from the Lemur host network position. The CRL path also used an unbounded cache, allowing attacker-controlled entries to persist and consume memory. The fix validates destinations, supports explicit trusted-host allowlists, and bounds the CRL cache. This issue is fixed in version 1.9.2.
Title Lemur: Post-authentication SSRF via certificate verification - attacker-controlled CRL and OCSP URLs in uploaded certificates
Weaknesses CWE-918
References
Metrics cvssV3_1

{'score': 6.3, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:L'}


Subscriptions

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cve-icon MITRE

Status: PUBLISHED

Assigner: GitHub_M

Published:

Updated: 2026-08-18T18:52:25.801Z

Reserved: 2026-06-16T15:13:28.165Z

Link: CVE-2026-55162

cve-icon Vulnrichment

No data.

cve-icon NVD

Status : Received

Published: 2026-08-18T19:16:58.217

Modified: 2026-08-18T19:16:58.217

Link: CVE-2026-55162

cve-icon Redhat

No data.

cve-icon OpenCVE Enrichment

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Weaknesses