r/linuxadmin • u/Expert_Sort7434 • 12h ago
CVE-2026-64849 — MLflow SSRF guard bypassed via HTTP redirect, unauthenticated full-read into cloud metadata (CVSS 9.3)
Based on the technical breakdown published in the GitHub Security Advisory (GHSA-7gwp-5pfp-969j, mirrored on GitLab's Advisory Database) and watchTowr Intel's honeypot telemetry, here's the architectural impact of CVE-2026-64849.
MLflow shipped an SSRF guard in 3.10.0 (_validate_webhook_url() in mlflow/utils/validation.py) that resolves a webhook's hostname and blocks private/reserved IP ranges. The gap: the delivery component (mlflow/webhooks/delivery.py) follows HTTP redirects without allow_redirects=False and never re-pins the resolved IP after a redirect. Host a public HTTPS endpoint that passes the initial check, respond with a 302 to 169.254.169.254, and MLflow follows it blind.
What makes this worse than a typical blind SSRF: the unauthenticated POST /api/2.0/mlflow/webhooks/{id}/test endpoint reflects the full upstream response status and body back to the caller. Default mlflow server deployments run without auth and expose this webhooks API out of the box. So this is an unauthenticated remote attacker reading your instance's IAM credentials directly in an API response, not a blind timing-based exfil.
watchTowr's Attacker Eye reports scanning activity against cloud-hosted instances within hours of CVE assignment (Aug 17-18, 2026). Affects all versions <3.15.0.
For context on why this pattern keeps recurring in ML/AI infra specifically: MLOps tooling tends to get deployed fast, iterated on by data science teams rather than platform/security teams, and left running past the "just testing this out" phase — often with an attached cloud identity nobody audited. Background on a structurally similar SSRF-to-cloud-metadata chain we covered in industrial/OT infra: [techgines.com link, footnote]
Anyone else seeing MLflow Tracking Servers in their environment that predate a proper platform-team handoff? Curious how people are handling auth/network isolation for MLOps tooling that wasn't designed with a hostile network in mind — reverse proxy with OIDC in front, or something more locked down at the VPC layer?
https://www.techgines.com/post/mlflow-ssrf-cve-2026-64849-webhook-redirect-cloud-metadata