---
id: "CVE-2026-103866"
kind: "vulnerability"
aliases: ["CVE-2026-103866"]
title: "Apache Sling Engine: request parser flaw enables HTTP request smuggling"
severity: "unknown"
cvss: null
epss: null
exploited: false
status: "open"
category: "package"
products: []
ecosystems: []
tags: ["aem", "apache-sling", "java", "package"]
not_affected_if: ["already-patched"]
published_at: "2026-11-05T13:17:07+00:00"
first_seen_at: "2026-11-05T13:39:09+00:00"
updated_at: "2026-11-05T13:40:09+00:00"
sources: [{"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-103866", "first_seen_at": "2026-11-05T13:39:09+00:00"}]
exploit_sources: []
---

# Apache Sling Engine: request parser flaw enables HTTP request smuggling

Apache Sling Engine's query and form parser accepts non-standard percent-escapes and wrong charsets, and keeps processing requests after such parse errors. This lets an attacker craft requests that a front-end proxy and Sling read differently, which can smuggle a second request past access controls.

_Summary, check and fix written by a model from the sources; labelled as such._

## How to check

- Check the Apache Sling Engine version in the project's dependency file or bundle manifest, looking for versions before `3.0.4`
- Confirm whether a reverse proxy or load balancer sits in front of the Sling-based application

## Fix

- Apache Sling Engine: upgrade to `3.0.4`

## Timeline

- 2026-11-05T13:39:09+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-103866

## From the sources

Inconsistent interpretation of HTTP requests ('HTTP Request/Response smuggling') vulnerability in Apache Sling Engine. The engine's query/form parser accepts non-standard percent-escapes, wrong charsets, and continues request processing on such errors.



This issue affects Apache Sling Engine: before 3.0.4.



Users are recommended to upgrade to version 3.0.4, which fixes the issue.

---

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