---
id: CVE-2026-55165
title: Lemur manages TLS certificate creation
summary: >-
  Lemur manages TLS certificate creation. Prior to 1.9.2, the JWT verifier in
  lemur/auth/service.py:130-137 used fetch_token_header to read
  header_data["alg"] from an unverified token and passed that
  attacker-controlled value to decode_wit…
severity: medium
cvss: 4.8
cvssVector: 'CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:N'
cwe:
  - CWE-347
vendor: lemur
product: lemur
affected:
  - lemur < 1.9.2
patched:
  - lemur 1.9.2
published: '2026-08-18'
updated: '2026-09-08'
sourceUpdated: '2026-09-08T21:02:26.047'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-55165'
references:
  - url: >-
      https://github.com/Netflix/lemur/commit/89898e665beed044cf7bd5927dfaa484e55bf242
    label: security-advisories@github.com
  - url: 'https://github.com/Netflix/lemur/releases/tag/v1.9.2'
    label: security-advisories@github.com
  - url: 'https://github.com/Netflix/lemur/security/advisories/GHSA-r9gp-7f88-9r54'
    label: security-advisories@github.com
  - url: 'https://github.com/Netflix/lemur/security/advisories/GHSA-r9gp-7f88-9r54'
    label: 134c704f-9b21-4f2e-91b3-4a467353bcc0
  - url: 'https://github.com/advisories/GHSA-r9gp-7f88-9r54'
tags:
  - nvd
  - ghsa
  - pip
epss: 0.00154
epssPercentile: 0.0488
ecosystem: pip
ingestedAt: '2026-06-26T16:43:14.204Z'
---

## Overview

Lemur manages TLS certificate creation. Prior to 1.9.2, the JWT verifier in lemur/auth/service.py:130-137 used fetch_token_header to read header_data["alg"] from an unverified token and passed that attacker-controlled value to decode_with_multiple_secrets. PyJWT 2.x rejects alg=none with the configured key, so the flaw is a defense-in-depth gap rather than a direct authentication bypass in the shipped configuration. The unpinned algorithm can become exploitable after an asymmetric-signing migration through algorithm confusion, and it weakens algorithm-based anomaly detection because the token chooses the recorded value. A separate disclosure of LEMUR_TOKEN_SECRET would also permit forged HS256 tokens, although that disclosure is an independent prerequisite. The fix introduces the server-controlled LEMUR_TOKEN_ALGORITHMS allowlist and defaults it to HS256. This issue is fixed in version 1.9.2.

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.

## Package advisory (CVE-2026-55165)

Affected packages:

- `lemur < 1.9.2`

Patched in:

- `lemur 1.9.2`

Source: https://github.com/advisories/GHSA-r9gp-7f88-9r54