CVE-2026-25403

Executive Summary

CVE-2026-25403 is an unauthenticated Broken Access Control vulnerability affecting the WordPress Ultimate Store Kit Elementor Addons plugin, with all versions up to and including 3.0.5 confirmed vulnerable. The flaw permits remote attackers to bypass authorization checks without any prior authentication, leading to partial confidentiality and integrity compromise of affected WordPress installations. Given the AV:N/AC:L/PR:N combination in the CVSS vector, this vulnerability is trivially exploitable over the network by any unauthenticated party, and the affected plugin is widely deployed in WooCommerce storefronts.

Technical Analysis

The vulnerability resides in the WordPress Ultimate Store Kit Elementor Addons plugin, version 3.0.5 and earlier. The root cause is classified under CWE-862 (Missing Authorization), indicating that the plugin fails to perform adequate permission checks before executing certain functionality.

Since the plugin extends Elementor — a popular WordPress page builder — the affected functionality is likely exposed through AJAX action hooks, REST API endpoints, or shortcode handlers that the plugin registers on page load. In WordPress plugin architecture, components that register callbacks for AJAX actions must explicitly enforce capability checks (e.g., current_user_can()) before processing requests. When such checks are absent or improperly implemented, any unauthenticated visitor can invoke the action by sending a crafted HTTP request.

The NVD description specifically confirms that the broken access control is unauthenticated, meaning the affected code path requires no user session, cookie, or authentication token. This distinguishes the vulnerability from lower-severity access control flaws that might only affect low-privileged subscribers or contributors.

The CVSS vector, scoring 6.5, indicates the following characteristics:

• Attack Vector: Network (AV:N) — The vulnerability is exploitable remotely over the network.
• Attack Complexity: Low (AC:L) — No special conditions need to be met; exploitation does not require race conditions or specific timing.
• Privileges Required: None (PR:N) — No authentication is required to exploit this flaw.
• User Interaction: None (UI:N) — The victim does not need to perform any action (e.g., clicking a link) for exploitation to succeed.
• Scope: Unchanged (S:U) — The compromise is contained to the vulnerable component, not extending to adjacent security boundaries.
• Confidentiality Impact: Low (C:L) — Some restricted information may be disclosed.
• Integrity Impact: Low (I:L) — Some data may be modified, but the impact is limited.
• Availability Impact: None (A:N) — The vulnerability does not directly affect service availability.

The low confidentiality and integrity scores suggest the vulnerable functionality is likely capable of leaking plugin configuration details or performing limited state changes (e.g., toggling settings, accessing order metadata) rather than achieving full database exfiltration or Remote Code Execution.

Exploitation Scenarios

Despite the absence of a public proof-of-concept, the exploitation chain for an unauthenticated broken access control vulnerability in a WordPress plugin follows a predictable trajectory:

Step 1: Reconnaissance

An attacker begins by scanning the internet for WordPress sites running the Ultimate Store Kit Elementor Addons plugin. The attacker uses Shodan dorks such as http.component:"WordPress" http.body:"ultimate-store-kit" or Google dorks like inurl:"wp-content/plugins/ultimate-store-kit" to identify candidate targets. The attacker also fingerprints the plugin version by requesting /wp-content/plugins/ultimate-store-kit/readme.txt or checking the Version header in the plugin's main PHP file.

Step 2: Endpoint Discovery

The attacker analyzes the plugin's source code (freely available from the WordPress plugin repository) to identify AJAX action hooks that lack current_user_can() or is_admin() checks. Typical discovery vectors include:

• Enumerating all functions hooked to wp_ajax_nopriv_* events, which are specifically designed to be callable by unauthenticated users.
• Reviewing the plugin's register_rest_route() calls for missing permission_callback arguments — a common WordPress REST API authorization gap.
• Searching for admin_post_nopriv handlers in the plugin's PHP files.

Step 3: Crafting the Exploit Request

The attacker constructs a crafted HTTP POST or GET request targeting the vulnerable endpoint. For AJAX-based handlers, this would take the form:

POST /wp-admin/admin-ajax.php HTTP/1.1
Host: target-site.com
Content-Type: application/x-www-form-urlencoded

action=some_vulnerable_action&nonce_value=any&parameter1=value1

If the vulnerable handler is exposed via the REST API, the request would target:

GET /wp-json/plugin-namespace/v1/vulnerable-endpoint?parameter=value HTTP/1.1
Host: target-site.com

The attacker includes a nonce parameter if the handler requires one, but since the vulnerability stems from missing authorization (not missing nonce verification), the nonce can typically be obtained from any public-facing page that embeds the plugin's scripts, or the check is entirely absent.

Step 4: Payload Execution

The attacker manipulates the request parameters to trigger the unauthorized action. For an integrity-impact scenario, the attacker might modify plugin settings, change displayed storefront content, or alter configuration options. For a confidentiality-impact scenario, the attacker might invoke a handler that returns protected data — such as WooCommerce order details, customer information, or plugin debug data — in the JSON/HTML response.

Step 5: Post-Exploitation

The attacker leverages the disclosed data for further attacks (e.g., credential stuffing with leaked customer emails) or persists the integrity changes to deface the storefront or manipulate product pricing display. The low integrity impact limits the attacker's capability to achieve full site takeover, but the attacker may chain this vulnerability with other flaws to escalate privileges.

Impact Assessment

Business Impact: The vulnerability carries a Medium severity rating (CVSS 6.5). For WooCommerce storefronts running the plugin, the immediate business risk stems from unauthorized data disclosure (customer order information if exposed) and limited content manipulation. E-commerce operations may experience degraded customer trust if product pages or checkout-related components are tampered with.

Affected Systems: All WordPress installations running Ultimate Store Kit Elementor Addons version ≤ 3.0.5. The plugin is an extension of the Elementor page builder, meaning sites that do not have Elementor active but have the plugin installed may still expose vulnerable code paths if the plugin registers hooks independently.

Blast Radius: The attack surface is every publicly accessible WordPress site with the vulnerable plugin installed. Since the vulnerability requires no authentication, the entire unauthenticated internet-facing attack surface is exposed, not just a subset of privileged users. However, the CVSS subscores (C:L/I:L/A:N) indicate the blast radius is contained — an attacker cannot achieve full database compromise or leverage this flaw for remote code execution directly.

CVSS Subscore Rationale: The Low Confidentiality impact suggests the attacker can access only limited information, likely plugin-specific data rather than the full WordPress database. The Low Integrity impact suggests limited write capability, possibly confined to plugin-managed options. The complete absence of availability impact indicates the vulnerability cannot be weaponized for denial-of-service.

Detection Guidance

The following detection rules assume the attacker's exploitation pattern involves HTTP requests to WordPress admin-facing endpoints (e.g., /wp-admin/admin-ajax.php) or REST API routes that do not match normal user behavior patterns.

Sigma Rule

title: Unauthenticated AJAX Request to Ultimate Store Kit Plugin Endpoints
id: 5a8c2f31-b8c4-4a7e-9d2a-1f6c4b9e8a22
status: experimental
description: Detects unauthenticated HTTP requests to WordPress AJAX endpoints associated with the Ultimate Store Kit Elementor Addons plugin.
references:
    - https://nvd.nist.gov/vuln/detail/CVE-2026-25403
author: Valtersit Threat Intelligence
date: 2026/01/15
logsource:
    category: webserver
    product: apache
    definition: 'WordPress site running Ultimate Store Kit Elementor Addons <= 3.0.5'
detection:
    selection_admin_ajax:
        cs-method: 'POST'
        cs-uri-query:
            - contains: 'admin-ajax.php'
        cs-uri-query|contains:
            - 'action=ultimate_store_kit'
            - 'action=uskt_'
            - 'action=store_kit'
    selection_rest_api:
        cs-uri-query|contains:
            - '/wp-json/ultimate-store-kit/'
            - '/wp-json/uskt/'
    selection_no_auth_cookie:
        cs-uri-query|contains:
            - 'wp_ajax_nopriv'
            - 'rest_route'
    filter_known_legit:
        cs-uri-query|contains:
            - 'action=heartbeat'
            - 'action=rest-nonce'
    condition: (selection_admin_ajax or selection_rest_api) and not filter_known_legit
level: high
tags:
    - attack.t1190
    - attack.initial_access
    - cve.2026.25403

YARA Rule

rule CVE_2026_25403_Ultimate_Store_Kit_Exploit
{
    meta:
        author = "Valtersit Threat Intelligence"
        date = "2026-01-15"
        description = "Detects exploitation attempts against WordPress Ultimate Store Kit Elementor Addons broken access control vulnerability"
        cve = "CVE-2026-25403"
        reference = "https://nvd.nist.gov/vuln/detail/CVE-2026-25403"
        severity = "medium"

    strings:
        $admin_ajax = "admin-ajax.php" ascii wide
        $action_param = "action=" ascii wide
        $plugin_slug = "ultimate-store-kit" ascii wide
        $plugin_slug_short = "uskt_" ascii wide
        $rest_route = "rest_route=" ascii wide
        $nopriv = "nopriv" ascii wide

    condition:
        uint16(0) == 0x3f3f and // HTTP response header
        (
            ($admin_ajax and $action_param) or
            ($rest_route and $plugin_slug) or
            ($plugin_slug_short and $action_param)
        ) and
        not ($nopriv and filesize < 100) // Exclude simple nonce fetch requests
}

Suricata IDS Rule

alert http any any -> $HOME_NET any (msg:"CVE-2026-25403 - Unauthenticated Access to Ultimate Store Kit AJAX Handler"; flow:to_server,established; http.uri; content:"/wp-admin/admin-ajax.php"; http.uri; pcre:"/action=(uskt_|ultimate_store_kit|store_kit)/i"; http.method; content:"POST"; classtype:attempted-admin; sid:202625403; rev:1; metadata:created_at 2026_01_15, updated_at 2026_01_15, cve CVE_2026_25403)

Elastic Detection

// Detect POST requests to admin-ajax.php with plugin-specific action parameters
// where the request lacks authentication cookies (unauthenticated access)
sequence by source.ip, destination.ip
  with maxspan=5m
  [ network where event.type == "start" and
      destination.port == 443 and
      http.request.method == "POST" and
      url.path contains "/wp-admin/admin-ajax.php" and
      url.query contains "action=uskt_" ]
  [ network where event.type == "end" and
      http.request.method == "POST" and
      url.path contains "/wp-admin/admin-ajax.php" and
      url.query contains "action=uskt_" and
      // Check for absence of WordPress auth cookies
      not any(http.request.headers["cookie"] like "*wordpress_logged_in_*") ]

Splunk SPL Query

index=web sourcetype=access_combined
| where like(uri_path, "%admin-ajax.php%")
    AND method = "POST"
    AND (like(form_data, "%action=uskt_%") OR like(form_data, "%action=ultimate_store_kit%") OR like(form_data, "%action=store_kit%"))
    AND NOT like(cookie, "%wordpress_logged_in_%")
| eval threat_severity = "medium"
| eval cve_id = "CVE-2026-25403"
| table _time, src_ip, dest_ip, method, uri_path, form_data, user_agent, cookie
| sort - _time

Wazuh OSSEC Rule

<group name="wordpress,">
  <rule id="100826" level="12">
    <decoded>wazuh</decoded>
    <if_sid>9310</if_sid>
    <match>admin-ajax.php</match>
    <regex>action=(uskt_|ultimate_store_kit|store_kit)</regex>
    <description>Detected unauthenticated AJAX request targeting Ultimate Store Kit plugin (CVE-2026-25403)</description>
    <group>cve-2026-25403,</group>
    <mitre>
      <id>T1190</id>
    </mitre>
  </rule>
</group>

Mitigation & Patch Guidance

Patch confidence: 2/4 (CLAIMED) — a single source (the CNA) claims a patched version exists; this has not been independently confirmed by multiple parties.

1) Immediate Mitigations (before applying patch)

• Disable the plugin: If maintaining storefront functionality is not critical, deactivate and remove the Ultimate Store Kit Elementor Addons plugin entirely until the patch is verified.
• Web Application Firewall (WAF) rules: Deploy temporary WAF rules to block HTTP requests targeting /wp-admin/admin-ajax.php with plugin-specific action parameters (e.g., action=uskt_*) from unauthenticated sources.
• Network-level ACLs: Restrict access to /wp-admin/admin-ajax.php from unknown IP addresses where business workflows permit. Since legitimate AJAX calls originate from the visitor's browser, blocking all external access may break storefront functionality.
• Monitor access logs: Actively search for anomalous POST requests to admin-ajax.php lacking WordPress authentication cookies.

2) Patch / Upgrade Steps

• The vendor fix claims version 3.0.7 resolves the vulnerability. Since the patch confidence is 2/4 (single-source claim), perform the following:
  1. Check for the latest version via the WordPress admin dashboard: Plugins → Installed Plugins → Ultimate Store Kit Elementor Addons → View version.
  2. Navigate to Dashboard → Updates and apply the plugin update to version 3.0.7 (or later).
  3. If the update is not available via the WordPress repository, download the latest version from the vendor's website or the Patchstack advisory page.
  4. After updating, verify the plugin's PHP files no longer contain unauthenticated AJAX hooks by reviewing the plugin's code for wp_ajax_nopriv_ handlers that lack current_user_can() checks.
• If version 3.0.7 is unavailable or cannot be installed, consider it a persistent risk and maintain the mitigations listed in section 1 indefinitely.

3) Long-Term Hardening

• Adopt a WordPress vulnerability management program: Subscribe to a WordPress vulnerability feed (e.g., Patchstack, WPScan) to receive immediate alerts for plugins used in the environment.
• Reduce plugin footprint: Review all installed WordPress plugins and remove any that are redundant. Fewer plugins = smaller attack surface.
• Implement the Principle of Least Privilege: Ensure only site administrators can modify plugin files, and restrict FTP/SFTP/SSH access to the WordPress installation directory.
• Enable WordPress auto-updates: Configure auto-update policies for minor plugin versions where testing permits, reducing the window of exposure for future vulnerabilities.
• Regular security assessments: Run periodic WordPress security scans (e.g., WPScan, Maldet) to detect vulnerable plugin versions and indicators of compromise.
• Server hardening: Enforce strong authentication (MFA) for WordPress admin accounts, and implement IP allowlisting for the WordPress administrative backend.

References

1. NVD Entry: https://nvd.nist.gov/vuln/detail/CVE-2026-25403 — Official National Vulnerability Database record containing the CVSS score, CWE classification, and vulnerability description.
2. Patchstack Advisory: https://patchstack.com/database/vulnerability/ultimate-store-kit-elementor-addons — Original CNA advisory confirming the vulnerability and the claimed 3.0.7 fix version. (Verify by searching the Patchstack database for "Ultimate Store Kit".)
3. WordPress Plugin Repository: https://wordpress.org/plugins/ultimate-store-kit-elementor-addons/ — Official plugin page where patched versions will be distributed.
4. CWE-862 Official Page: https://cwe.mitre.org/data/definitions/862.html — MITRE Common Weakness Enumeration entry detailing the missing authorization weakness class.

Threat Actor Campaigns / Exploit-in-the-Wild Evidence: At the time of writing, no known threat actor campaigns or exploit-in-the-wild activity have been publicly documented for CVE-2026-25403. The vulnerability is not listed on the CISA Known Exploited Vulnerabilities (KEV) catalog. However, given the commonality of broken access control flaws in WordPress plugins and the availability of the plugin's source code for analysis, attackers are likely to develop exploits rapidly following disclosure. Enterprise security teams should prioritize patching before scanning campaigns commoditize this vulnerability.