---
id: CVE-2026-48157
title: Slim has Reflected XSS in the HtmlErrorRenderer
summary: Slim has Reflected XSS in the HtmlErrorRenderer
severity: medium
cvss: 6.1
cwe:
  - CWE-79
vendor: slim
product: slim/slim
ecosystem: composer
affected:
  - 'slim/slim >= 4.4.0, <= 4.15.1'
patched:
  - slim/slim 4.15.2
published: '2026-06-23'
updated: '2026-06-23'
source: GHSA
sourceUrl: 'https://github.com/advisories/GHSA-53h4-8rc4-f539'
references:
  - url: 'https://github.com/slimphp/Slim/security/advisories/GHSA-53h4-8rc4-f539'
  - url: 'https://nvd.nist.gov/vuln/detail/CVE-2026-48157'
  - url: 'https://github.com/slimphp/Slim/releases/tag/4.15.2'
  - url: 'https://github.com/advisories/GHSA-53h4-8rc4-f539'
tags:
  - ghsa
  - composer
epss: 0.00167
epssPercentile: 0.0637
ingestedAt: '2026-06-26T16:43:14.611Z'
---

## Overview

### Impact

If an application uses `HttpException::setTitle()` and/or `setDescription()` to include untrusted/request-derived data in the error title or description (e.g. `"No products found matching '{$query}'."`), an attacker could inject arbitrary HTML/JavaScript that executes in the victim's browser when they encounter an HTML error page generated by Slim.

The vulnerability is present even with `displayErrorDetails = false` as the unescaped title and description are rendered on this error path.

Built-in exceptions (`HttpNotFoundException`, `HttpBadRequestException`, etc.) ship plain-text defaults, so a vanilla Slim app with no user code is not exploitable. Only applications that feed untrusted data into `setTitle()` and/or `setDescription()` are affected.

### Patches

The issue is fixed in 4.15.2.

### Workarounds

Without upgrading, applications can:

- Avoid passing untrusted/request-derived data into `HttpException::setTitle()` and `setDescription()`. Use static, plain-text error copy instead.
- Register a custom error renderer (an `ErrorRendererInterface` implementation, or a subclass of `HtmlErrorRenderer` that escapes the title and description) for the HTML media type.

### Acknowledgments

Slim is grateful to and thanks GitHub user [0xEr3n](https://github.com/0xEr3n) for reporting this issue.

### Resources

- CWE-79: https://cwe.mitre.org/data/definitions/79.html

## Affected packages

- `slim/slim >= 4.4.0, <= 4.15.1`

## Remediation

Upgrade to a patched release:

- `slim/slim 4.15.2`