CVE-2026-14440 Cloudflare Universal SSL automatically managed CAA RRset supersedes customer-configured CAA records
Cloudflare Universal SSL overrides customer CAA records, bypassing RFC 8657 protections and potentially allowing attacker-controlled certificate issuance for MITM attacks.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- None listed
What is CVE-2026-14440?
CVE-2026-14440 is a high-severity vulnerability in Cloudflare Universal SSL, published on 1 Jul 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Official description
Description:
To issue and renew TLS certificates on behalf of customers, Cloudflare's Universal SSL feature automatically manages the CAA RRset for the customer's zone. This auto-managed RRset is permissive by design (e.g. 'issue "letsencrypt.org"' without parameters). On Universal SSL zones, Cloudflare's authoritative DNS serves this auto-managed RRset at query time, superseding any customer-configured CAA records on the zone. When a customer publishes a stricter CAA record using the RFC 8657 accounturi or validationmethods parameters, the Certificate Authority does not observe those parameters when evaluating the served RRset under RFC 8659. As a result, the RFC 8657 account-binding and validation-method-binding protections are not enforced end-to-end on Universal SSL zones. Successful exploitation could result in issuance of a browser-trusted TLS certificate to an attacker, enabling MITM against the affected domain.
Exploitation is non-trivial in practice: an attacker would need to hold an ACME account at one of the Certificate Authorities in the served CAA RRset and to simultaneously satisfy domain control validation across the multiple geographically distinct Network Perspectives the CA relies on for Multi-Perspective Issuance Corroboration. Cloudflare prefixes are anycast-announced from hundreds of locations globally, raising the bar against single-vantage-point BGP hijacks. Any resulting misissuance of a browser-trusted certificate is subject to Certificate Transparency logging required by major browsers, and would be visible to CT monitoring.
Mitigation:
Customers requiring strict RFC 8657 enforcement need to disable Universal SSL on the affected zone.
Universal SSL's automatic CAA management and customer-set RFC 8657 accounturi and validationmethods enforcement are mutually exclusive by the nature of the issue, so there is no in-product workaround that preserves both.
Certificate Transparency monitoring is recommended for all customers as a general detection control.
Credits:
David Osipov (ORCID: https://orcid.org/0009-0005-2713-9242), independent researcher
Weakness: CWE-693
Which versions are affected by CVE-2026-14440?
How do I fix CVE-2026-14440?
No fix has been published for CVE-2026-14440 yet. Limit exposure of the affected software until one is available.
Is CVE-2026-14440 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-14440 exists.
Public exploit code: 1 proofs of concept on GitHub.
Sources
Also known as GHSA-vrv9-rjp4-w93c.