NVD - CVE-2026-14440
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Information Technology Laboratory
National Vulnerability Database
National Vulnerability Database
NVD
Vulnerabilities
CVE-2026-14440<br>Detail
Awaiting Enrichment
This CVE record has been marked for NVD enrichment efforts.
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
Metrics
 
CVSS Version 4.0
CVSS Version 3.x
CVSS Version 2.0
NVD enrichment efforts reference publicly available information to associate<br>vector strings. CVSS information contributed by other sources is also<br>displayed.
CVSS 4.0 Severity and Vector Strings:
NIST: NVD
N/A
NVD assessment<br>not yet provided.
CNA: Cloudflare, Inc.
CVSS-B 7.6 HIGH
Vector: 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<br>CVSS v4.0 Severity and Metrics:CVSS-B: 7.6 HIGHVector: AV:A/AC:H/AT:P/PR:N/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:NAttack Vector (AV): AdjacentAttack Complexity (AC): HighAttack Requirements (AT): PresentPrivileges Required (PR): NoneUser Interaction (UI): NoneVulnerable System Confidentiality (VC): HighVulnerable System Integrity (VI): HighVulnerable System Availability (VA): NoneSubsequent System Confidentiality (SC): NoneSubsequent System Integrity (SI): NoneSubsequent System Availability (SA): None "/>
CVSS 3.x Severity and Vector Strings:
NIST: NVD
Base<br>Score: N/A
NVD assessment<br>not yet provided.
ADP: CISA-ADP
Base<br>Score: 6.8 MEDIUM
Vector: CVSS:3.1/AV:A/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N<br>CVSS v3.1 Severity and Metrics: Base Score: 6.8 MEDIUM Vector: AV:A/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N Impact Score: 5.2 Exploitability Score: 1.6 Attack Vector (AV): Adjacent Attack Complexity (AC): High Privileges Required (PR): None User Interaction (UI): None Scope (S): Unchanged Confidentiality (C): High Integrity (I): High Availability (A): None "/>
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CVSS 2.0 Severity and Vector Strings:
NIST: NVD
Base<br>Score: N/A
NVD assessment<br>not yet provided.
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