Netflix Lemur up to 1.9.1 verify.py verify_string certificate validation

Summaryinfo

A vulnerability marked as problematic has been reported in Netflix Lemur up to 1.9.1. This affects the function verify_string of the file lemur/certificates/verify.py. This manipulation causes certificate validation. This vulnerability is tracked as CVE-2026-55162. The attack is possible to be carried out remotely. No exploit exists.

Detailsinfo

A vulnerability has been found in Netflix Lemur up to 1.9.1 and classified as problematic. Affected by this vulnerability is the function verify_string of the file lemur/certificates/verify.py. The manipulation with an unknown input leads to a certificate validation vulnerability. The CWE definition for the vulnerability is CWE-295. The product does not validate, or incorrectly validates, a certificate. As an impact it is known to affect integrity. The summary by CVE is:

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.

It is possible to read the advisory at github.com. This vulnerability is known as CVE-2026-55162 since 06/16/2026. The exploitation appears to be difficult. The attack can be launched remotely. The exploitation doesn't need any form of authentication. Technical details of the vulnerability are known, but there is no available exploit. The attack technique deployed by this issue is T1587.003 according to MITRE ATT&CK.

Upgrading to version 1.9.2 eliminates this vulnerability.

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Productinfo

Vendor

• Netflix

Name

• Lemur

Version

• 1.9.0
• 1.9.1

Website

• Product: https://github.com/Netflix/lemur/

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