CVE-2026-14440 (GCVE-0-2026-14440)
Vulnerability from cvelistv5 – Published: 2026-07-01 22:35 – Updated: 2026-07-02 13:13
VLAI
Title
Cloudflare Universal SSL automatically managed CAA RRset supersedes customer-configured CAA records
Summary
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
Severity
SSVC
Exploitation: none
Automatable: no
Technical Impact: total
CISA Coordinator (v2.0.3)
CWE
- CWE-358 - Improperly Implemented Security Check for Standard
Assigner
References
Impacted products
1 product
| Vendor | Product | Version | |
|---|---|---|---|
| Cloudflare | Universal SSL |
Affected:
0 , ≤ current
(custom)
|
Credits
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This auto-managed RRset is permissive by design (e.g. \u0027issue \\\"letsencrypt.org\\\"\u0027 without parameters). On Universal SSL zones, Cloudflare\u0027s 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.\u003c/p\u003e\u003cbr\u003e\u003cp\u003eExploitation 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.\u003c/p\u003e\u003cp\u003e\u003cbr\u003e\u003c/p\u003e\u003cp\u003e\u003cspan\u003e\u003cb\u003eMitigation:\u0026nbsp;\u003c/b\u003e\u003c/span\u003e\u003c/p\u003e\u003cp\u003e\u003cspan\u003eCustomers requiring strict RFC 8657 enforcement need to disable Universal SSL on the affected zone.\u003c/span\u003e\u003c/p\u003e\u003cp\u003e\u003cspan\u003eUniversal SSL\u0027s 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.\u0026nbsp;\u003c/span\u003e\u003c/p\u003e\u003cp\u003e\u003cspan\u003eCertificate Transparency monitoring is recommended for all customers as a general detection control.\u003c/span\u003e\u003c/p\u003e\u003cp\u003e\u003cb\u003e\u003c/b\u003e\u003cbr\u003e\u003c/p\u003e\u003cp\u003e\u003cspan\u003e\u003cb\u003eCredits:\u003c/b\u003e\u003c/span\u003e\u003c/p\u003e\u003cp\u003e\u003cspan\u003eDavid Osipov (ORCID: https://orcid.org/0009-0005-2713-9242), independent researcher\u003c/span\u003e\u003c/p\u003e\u003cp\u003e\u003cb\u003e\u003c/b\u003e\u003cbr\u003e\u003c/p\u003e\u003cbr\u003e\", \"base64\": false}]}], \"providerMetadata\": {\"orgId\": \"a22f1246-ba21-4bb4-a601-ad51614c1513\", \"shortName\": \"cloudflare\", \"dateUpdated\": \"2026-07-01T22:35:10.353Z\"}}}",
"cveMetadata": "{\"cveId\": \"CVE-2026-14440\", \"state\": \"PUBLISHED\", \"dateUpdated\": \"2026-07-02T13:13:36.355Z\", \"dateReserved\": \"2026-07-01T22:20:45.895Z\", \"assignerOrgId\": \"a22f1246-ba21-4bb4-a601-ad51614c1513\", \"datePublished\": \"2026-07-01T22:35:10.353Z\", \"assignerShortName\": \"cloudflare\"}",
"dataType": "CVE_RECORD",
"dataVersion": "5.2"
}
}
}
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Experimental. This forecast is provided for visualization only and may change without notice. Do not use it for operational decisions.
Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.
Sightings
| Author | Source | Type | Date | Other |
|---|
Nomenclature
- Seen: The vulnerability was mentioned, discussed, or observed by the user.
- Confirmed: The vulnerability has been validated from an analyst's perspective.
- Published Proof of Concept: A public proof of concept is available for this vulnerability.
- Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
- Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
- Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
- Not confirmed: The user expressed doubt about the validity of the vulnerability.
- Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.
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