CVE-2026-71303: Lemur manages TLS certificate creation

Routine

HIGH 7.7

CVE-2026-71303 is a high-severity flaw (CVSS 7.7) affecting affected software. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

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 passe

Why this priority

High severity
CISA SSVC: public proof of concept

A fixed release or distro patch exists.

Risk facts

CVSS score	7.7 (High)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	Low
User interaction	None
EPSS exploit chance	0.3% (top 81%)
CISA exploited list	No
Weakness	CWE-918
Published	2026-08-18
Last modified	2026-10-22

Publisher (CNA): GitHub, Inc.

Last updated 2026-10-22 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Timeline

2026-08-18Published CVE record published
2026-10-22 22:10 UTCUpdated Record last modified

Exact fixes by distribution

Python (pip) · lemur · FIXED · 1.9.3 · vulnerable: <= 1.9.2 · source

pip install --upgrade "lemur>=1.9.3" pip show lemur

Fedora 46 · wasmedge · FIXED · 0.18.1-1.fc46 · FEDORA-2026-4c27216e39 · source

sudo dnf upgrade --advisory=FEDORA-2026-4c27216e39

Public exploits and detection

Public code exists for this CVE. Treat unpatched systems as at risk, and only run PoCs in a lab.

Write-up: github.com/Netflix/lemur/security/advisories/GHSA-v5rc-cpwc-cfpr

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2026-71303?

No fixed release is listed yet. Watch the vendor advisory and apply any mitigation shown on this page.

Is CVE-2026-71303 being exploited?

CVE-2026-71303 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2026-71303 affect?

CVE-2026-71303 affects affected software. Severity is high (CVSS 7.7). 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

How urgent is CVE-2026-71303?

Priority 35/100. High severity; CISA SSVC: public proof of concept

References

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