Vulnerability · Published Aug 18, 2026 · Assigned by GitHub_M
CVE-2026-70666Lemur: Server-Side Request Forgery via the ACME client following server-controlled URLs
High 7.4
In plain English
A high-severity server-side request forgery in lemur from Netflix. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.2% (higher than 12% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.
Official description
Lemur manages TLS certificate creation. Prior to 1.9.3, an authority-role member could update acme_url through PUT /api/1/authorities/ without revalidation and direct setup_acme_client_no_retry to an attacker-controlled ACME server. ACME directory and order responses contain newNonce, newOrder, authorizations, and finalize URLs chosen by that server. The Lemur ClientV2 followed those URLs without requiring their host to match the configured directory host, allowing JWS-signed requests to internal services or cloud metadata endpoints. The issue required an ACME authority and a user authorized for that authority, but did not require global administrator privileges. The fix revalidates updates and introduces _PinnedClientNetwork to enforce a single allowed host for the complete ACME flow. This issue is fixed in version 1.9.3.
Affected packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| PyPI | lemur | 1.9.3 | GHSA-xpmj-wjcp-6pww |
| PyPI | lemur | 1.9.3 | PYSEC-2026-3680 |
Affected products (as reported)
Weakness: CWE-918 · Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:L/I:L/A:L
References
- https://github.com/Netflix/lemur/security/advisories/GHSA-xpmj-wjcp-6pww x_refsource_CONFIRM
- https://github.com/Netflix/lemur/commit/6dcb19b6d6004e97796d6a0344b130b2ba57f050 x_refsource_MISC
- https://github.com/Netflix/lemur/releases/tag/v1.9.3 x_refsource_MISC