---
description: Cloudflare WAF managed rulesets 2026-04-07 release
title: WAF Release - 2026-04-07
image: https://developers.cloudflare.com/changelog/post/2026-04-07-waf-release/og.png?v=93f8d59d1a201ba6
---

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April 7, 2026

## WAF Release - 2026-04-07

[WAF](https://developers.cloudflare.com/waf/)

Copy as Markdown| [View as Markdown](https://developers.cloudflare.com/changelog/post/2026-04-07-waf-release/index.md)| [Agent setup](https://developers.cloudflare.com/agent-setup/)

This week's release introduces new detections for a critical Remote Code Execution (RCE) vulnerability in MCP Server (CVE-2026-23744), alongside targeted protection for an authentication bypass vulnerability in SolarWinds products (CVE-2025-40552). Additionally, this release includes a new generic detection rule designed to identify and block Cross-Site Scripting (XSS) injection attempts leveraging "OnEvent" handlers within HTTP cookies.

**Key Findings**

- MCP Server (CVE-2026-23744): A vulnerability in the Model Context Protocol (MCP) server implementation where malformed input payloads can trigger a memory corruption state, allowing for arbitrary code execution.
- SolarWinds (CVE-2025-40552): A critical flaw in the authentication module allows unauthenticated attackers to bypass security filters and gain unauthorized access to the management console due to improper identity token validation.
- XSS OnEvents Cookies: This generic rule identifies malicious event handlers (such as onload or onerror) embedded within HTTP cookie values.

**Impact**

Successful exploitation of the MCP Server and SolarWinds vulnerabilities could allow unauthenticated attackers to execute arbitrary code or gain administrative control, leading to a full system takeover. Additionally, the new generic XSS detection prevents attackers from leveraging browser event handlers in cookies to hijack user sessions or execute malicious scripts.

| Ruleset | Rule ID | Legacy Rule ID | Description | Previous Action | New Action | Comments |
| --- | --- | --- | --- | --- | --- | --- |
| Cloudflare Managed Ruleset | ...0aa410af | N/A | Generic Rules - Command Execution - 5 - Body | Log | Disabled | This is a new detection. |
| Cloudflare Managed Ruleset | ...9131ec2f | N/A | Generic Rules - Command Execution - 5 - Header | Log | Disabled | This is a new detection. |
| Cloudflare Managed Ruleset | ...551eb9e5 | N/A | Generic Rules - Command Execution - 5 - URI | Log | Block | This is a new detection. |
| Cloudflare Managed Ruleset | ...d46229eb | N/A | MCP Server - Remote Code Execution - CVE:CVE-2026-23744 | Log | Block | This is a new detection. |
| Cloudflare Managed Ruleset | ...a864b9c2 | N/A | XSS - OnEvents - Cookies | Log | Block | This is a new detection. |
| Cloudflare Managed Ruleset | ...9712a863 | N/A | SQLi - Evasion - Body | Log | Disabled | This is a new detection. |
| Cloudflare Managed Ruleset | ...40732d48 | N/A | SQLi - Evasion - Headers | Log | Disabled | This is a new detection. |
| Cloudflare Managed Ruleset | ...e68a99b5 | N/A | SQLi - Evasion - URI | Log | Disabled | This is a new detection. |
| Cloudflare Managed Ruleset | ...3e8143d2 | N/A | SQLi - LIKE 3 - Body | Log | Disabled | This is a new detection. |
| Cloudflare Managed Ruleset | ...70e7fb97 | N/A | SQLi - LIKE 3 - URI | Log | Disabled | This is a new detection. |
| Cloudflare Managed Ruleset | ...4c538bd9 | N/A | SQLi - UNION - 2 - Body | Log | Disabled | This is a new detection. |
| Cloudflare Managed Ruleset | ...61c439c9 | N/A | SQLi - UNION - 2 - URI | Log | Disabled | This is a new detection. |
| Cloudflare Managed Ruleset | ...cf33ea10 | N/A | SolarWinds - Auth Bypass - CVE:CVE-2025-40552 | Log | Block | This is a new detection. |

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