CVE-2026-14440
Cloudflare Universal SSL automatically managed CAA RRset supersedes customer-configured CAA records
- Published
- Updated
- Reserved
- Assigned by
- cloudflare
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
Public exploit
2 references of the record are tagged as an exploit or proof of concept: anyone can try it against an unpatched system. CISA's SSVC rates its exploitation: a proof of concept is public.
- https://david-osipov.vision/en/blog/cybersecurity/cloudflare-ssl-mitm-flaw-2026/ (opens in a new tab)technical-descriptionexploit
- https://zenodo.org/records/18330221 (opens in a new tab)technical-descriptionexploit
Timeline
ID reserved
By cloudflare
Published
- 1 day later
· 1 day later
Record updated
Changes after publication (a new score, a public exploit, EPSS crossing 1, 10 or 50 %, leaving KEV) are kept since November 2026; earlier ones are not known.
Scores
| Scored by | CVSS | Score | Vector |
|---|---|---|---|
| cloudflareCNA (assigner) | 4.0 | High7.6 | CVSS:4.0/AV:A/AC:H/AT:P/PR:N/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N |
| CISA-ADPADP (enrichment) | 3.1 | Medium6.8 | CVSS:3.1/AV:A/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N |
| NVDNVD · Awaiting Analysis | 4.0 | High7.6 | CVSS:4.0/AV:A/AC:H/AT:P/PR:N/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X |
- EPSS (exploitation in 30 days)
- 0.20% · top 90% of all CVEs (7 Nov 2026)
- CISA SSVC
- Exploitation: poc · Automatable: no · Technical impact: total
The list uses the assigner's score when there is one, then CISA's, then NVD's: High 7.6.
Weakness
Affected products
- affected ≤ current
What to do
Solution: 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.
References (8)
- https://developers.cloudflare.com/ssl/edge-certificates/caa-records/ (opens in a new tab)
- https://developers.cloudflare.com/ssl/edge-certificates/universal-ssl/limitations/ (opens in a new tab)
- https://www.rfc-editor.org/rfc/rfc8657 (opens in a new tab)
- https://www.rfc-editor.org/rfc/rfc8659 (opens in a new tab)
- https://david-osipov.vision/en/blog/cybersecurity/cloudflare-ssl-mitm-flaw-2026/ (opens in a new tab)technical-descriptionexploit
- https://community.cloudflare.com/t/critical-security-gap-cloudflare-must-fully-support-rfc-8657-caa/799999/10 (opens in a new tab)related
- https://community.cloudflare.com/t/universal-ssl-exposes-domains-to-bgp-leaks-re-venezuela-analysis/879930 (opens in a new tab)related
- https://zenodo.org/records/18330221 (opens in a new tab)technical-descriptionexploit
Sources
The same CVE in the primary databases and aggregators, to check against.
- CVE.org record (opens in a new tab)
- CVE List JSON (GitHub) (opens in a new tab)
- NVD (opens in a new tab)
- FIRST EPSS (opens in a new tab)
- OSV.dev (opens in a new tab)
- GitHub Advisories (opens in a new tab)
- CIRCL Vulnerability-Lookup (opens in a new tab)
Badge for a README or a ticket
[](https://trackcve.app/cve/CVE-2026-14440)Record last updated .