CVE-2026-39749

Executive Summary

CVE-2026-39749 is a Broken Access Control vulnerability (CWE-862) affecting the "App for Cloudflare" WordPress plugin in versions 1.10.1 and below. The flaw allows an authenticated low-privileged user to perform unauthorized actions, resulting in a high integrity impact while confidentiality and availability remain unaffected. No public proof-of-concept, Nuclei template, or exploit code currently exists, and no vendor patch has been released.

Technical Analysis

The vulnerability resides in the "App for Cloudflare" plugin, a WordPress component that integrates site functionality with Cloudflare services. The NVD description identifies a "Subscriber Broken Access Control" issue, indicating that the missing authorization check is scoped to the plugin's handling of Subscriber-level (or lower) users. In WordPress, the Subscriber role is the lowest authenticated role, typically limited to profile management.

CWE-862 (Missing Authorization) describes a scenario where a function or endpoint does not verify that the requesting user holds the required capability before executing a privileged action. In the context of this plugin, the attacker must be authenticated (PR:L) — the CVSS vector confirms the attack requires low privileges, consistent with an authenticated Subscriber. The AC:L rating indicates no special conditions or elevated complexity are needed to trigger the fault.

The CVSS vector (AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:N) frames the impact precisely: no confidentiality loss and no availability loss, but high integrity impact. This means the flaw permits modification of data or configuration — likely plugin settings, Cloudflare zone configuration, or cached content — without proper authorization checks. The scope remains unchanged (S:U), so the impact is contained within the plugin/application context rather than spilling into the underlying operating system or other independent components.

The attack surface is the plugin's exposed WordPress endpoints (admin-ajax.php handlers, REST API routes, or admin-post.php actions) that process user-supplied requests. Because the plugin integrates with an external service (Cloudflare), improper authorization may allow a Subscriber to manipulate Cloudflare-related settings or trigger API calls on behalf of the site. The exact endpoint names, function names, and parameter structure are not disclosed in the available description, and no public advisory provides code-level detail.

The absence of a patch (0/4 confidence) and the lack of CVE-specific information from the vendor means the exact vulnerable code path cannot be pinpointed from public sources. The analysis is therefore constrained to the vulnerability class: a missing capability check or nonce validation failure on a plugin action that should be restricted to Administrator or higher roles.

Exploitation Scenarios

No public PoC is available; the attack chain below is inferred from the vulnerability class (CWE-862) and the CVSS vector.

1. Reconnaissance / Target Identification: The attacker identifies a WordPress site running the "App for Cloudflare" plugin version 1.10.1 or earlier. Plugin enumeration can be performed via public resources such as the WordPress plugin directory, HTML source (e.g., /wp-content/plugins/ paths), or passive fingerprinting. The attacker registers or compromises a Subscriber-level account, which is trivially available on sites that permit open registration.

2. Triggering the Flaw: Once authenticated as a Subscriber, the attacker sends a crafted request to a plugin endpoint that performs a privileged action but lacks an authorization check. Because the plugin fails to verify the user's capability (e.g., manage_options or a plugin-specific capability), the request is processed regardless of the low privilege level. The exact endpoint is not publicly documented; the flaw class implies the endpoint accepts parameters that modify plugin or Cloudflare-related state.

3. Payload / Execution Method: At the vulnerability-class level, the attacker submits a request (e.g., via HTTP GET/POST to an admin-ajax or REST route) with parameters that instruct the plugin to alter its configuration. The request does not require UI interaction (UI:N), meaning it can be automated and repeated. No specific parameter names are available in the provided data; the attack relies on the missing authorization gate rather than a memory-corruption or injection primitive.

4. Post-Exploitation Impact: Successful exploitation yields an integrity-only impact: the attacker can modify data that the affected component controls. Given the plugin's Cloudflare integration, this could include changing settings that affect CDN behavior, cache rules, or domain configuration. The confidentiality of data is not directly compromised, and availability is not impacted per the CVSS vector. The attacker cannot escalate to full site takeover through this CVE alone, but the unauthorized modification may facilitate further attacks or persistent misconfiguration.

Impact Assessment

The CVSS score of 6.5 (Medium) reflects a network-accessible flaw requiring low privileges. The subscores clarify the impact: Integrity:High (I:H) means the attacker can modify protected data; Confidentiality:None (C:N) and Availability:None (A:N) mean no data exposure or service disruption. The scope is Unchanged (S:U), so the blast radius is limited to the plugin and its managed resources.

Business impact includes unauthorized configuration changes to Cloudflare-related settings, which may degrade security posture (e.g., disabling protections), alter content delivery, or create conditions for follow-on attacks. Affected systems are WordPress installations running the vulnerable plugin version. The attack does not require user interaction (UI:N), enabling scalable exploitation across many targets. Blast radius is moderate for a single site but potentially large across an estate of WordPress deployments. The EPSS score is not yet available; no known exploitation in the wild has been reported, and the CVE is not in CISA KEV.

Detection Guidance

Sigma Rule

title: App for Cloudflare Broken Access Control Subscriber Exploitation Attempt
id: 8f4a2b1c-3d5e-6f7a-8b9c-0d1e2f3a4b5c
status: experimental
description: Detects unauthorized requests from low-privileged WordPress users targeting App for Cloudflare plugin endpoints, indicating CVE-2026-39749 exploitation.
references:
  - https://nvd.nist.gov/vuln/detail/CVE-2026-39749
author: Threat Intelligence
date: 2026-04-01
tags:
  - attack.initial_access
  - attack.t1190
  - cve.2026.39749
logsource:
  category: webserver
  product: apache
  service: access
detection:
  selection:
    cs-method:
      - 'POST'
      - 'GET'
    cs-uri-query|contains:
      - 'app-for-cloudflare'
      - 'cloudflare'
  condition: selection
fields:
  - c-ip
  - cs-uri
  - cs-uri-query
  - sc-status
falsepositives:
  - Legitimate administrator activity on the plugin settings pages
level: medium

YARA Rule

rule CVE_2026_39749_App_for_Cloudflare_BAC
{
    meta:
        description = "Detects App for Cloudflare plugin versions <= 1.10.1 vulnerable to broken access control (CVE-2026-39749)"
        author = "Threat Intelligence"
        date = "2026-04-01"
        reference = "https://nvd.nist.gov/vuln/detail/CVE-2026-39749"
        cve = "CVE-2026-39749"

    strings:
        $plugin_slug = "app-for-cloudflare" ascii wide nocase
        $plugin_header = "Plugin Name: App for Cloudflare" ascii wide nocase
        $version_le = /Version:\s*1\.(10\.[01]|[0-9]\.)/ ascii wide

    condition:
        (uint16(0) == 0x3C3F or uint16(0) == 0x2F2A) and
        any of ($plugin_slug, $plugin_header) and $version_le
}

Suricata IDS Rule

alert http any any -> any any (msg:"CVE-2026-39749 App for Cloudflare Broken Access Control Exploitation Attempt"; flow:established,to_server; http.method; content:"POST"; http.uri; content:"app-for-cloudflare"; nocase; http.uri; content:"cloudflare"; nocase; http.header; content:"Cookie"; nocase; reference:cve,2026-39749; classtype:attempted-user; sid:2026397490; rev:1;)

Elastic Detection

network where
  http.request.method in ("POST", "GET") and
  http.request.uri : ("*app-for-cloudflare*" or "*cloudflare*") and
  http.response.status_code in (200, 302) and
  user.name : ("subscriber" or "subscriber_*")

Splunk SPL Query

index=web sourcetype=access_combined
| search (method=POST OR method=GET)
| search uri_path="*app-for-cloudflare*" OR uri_path="*cloudflare*"
| eval is_subscriber=if(match(user, "(?i)subscriber"), 1, 0)
| where is_subscriber=1 AND status IN (200, 302)
| stats count values(uri_path) as uris by src_ip, user, status
| where count > 5

Wazuh OSSEC Rule

<group name="web,wordpress,cve-2026-39749">
  <rule id="202639749" level="10" frequency="5" timeframe="300">
    <if_matched_sid>31103</if_matched_sid>
    <match>app-for-cloudflare|cloudflare</match>
    <description>CVE-2026-39749: Multiple requests to App for Cloudflare plugin endpoints from low-privileged user - possible broken access control exploitation</description>
    <mitre>
      <id>T1190</id>
    </mitre>
    <group>cve_2026_39749,</group>
  </rule>
</group>

Mitigation & Patch Guidance

Patch confidence: 0/4 (UNPATCHED — no patch evidence from any tracked source).

1. Immediate Mitigations:

   • Restrict user registration to prevent arbitrary Subscriber account creation if not required.
   • Enforce strict capability checks on all plugin-related actions via a custom WordPress plugin snippet, but this is a temporary workaround and may break functionality.
   • Deploy a Web Application Firewall (WAF) rule to block requests from low-privileged users to plugin endpoints (e.g., match on the plugin slug in the URI and session role).
   • Monitor access logs for anomalous requests to the plugin's admin-ajax or REST routes originating from non-administrator accounts.

2. Patch/Upgrade Steps:

   • No vendor patch is available. Disable and remove the "App for Cloudflare" plugin until an official fix is released.
   • Alternatively, isolate the plugin on a staging environment and monitor the vendor's release notes for a version beyond 1.10.1.

3. Long-term Hardening:

   • Implement role-based access control reviews and ensure third-party plugins enforce capability checks (current_user_can) and nonce validation on all state-changing actions.
   • Adopt a vulnerability management program that tracks plugin versions and applies updates promptly.
   • Use least-privilege principles for WordPress roles and consider disabling subscriber-level accounts where not needed.
   • Monitor CVE databases and vendor advisories for the release of a patched version.

References

• NVD Entry: https://nvd.nist.gov/vuln/detail/CVE-2026-39749
• CWE-862: Missing Authorization: https://cwe.mitre.org/data/definitions/862.html
• MITRE ATT&CK T1190: Exploit Public-Facing Application: https://attack.mitre.org/techniques/T1190/
• WordPress Plugin Security Best Practices: https://developer.wordpress.org/plugins/security/
• CISA KEV Catalog: https://www.cisa.gov/known-exploited-vulnerabilities-catalog (CVE-2026-39749 not listed as of publication)
• No known threat actor campaigns or exploit-in-the-wild evidence associated with this CVE at the time of writing.