# CVE-2026-48157: Slim has Reflected XSS in the HtmlErrorRenderer

> Attackers can inject JavaScript via unescaped error titles in Slim framework if developers pass untrusted data to exception setters.

- **Severity:** Medium 6.1 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** A user has to click or open something
- **Fix available:** Yes
- **Published:** 15 Jun 2026
- **Updated:** 16 Jun 2026
- **Also known as:** GHSA-53h4-8rc4-f539

## What is CVE-2026-48157?

CVE-2026-48157 is a medium-severity cross-site scripting vulnerability in slimphp Slim, published on 15 Jun 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.

### Official description

Slim is a PHP micro framework that enables users to write simple web applications and APIs. In versions 4.4.0 through 4.15, 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. The issue has been fixed in 4.15.2. If developers are unable to immediately update their applications, they can work around this issue by avoiding passing untrusted/request-derived data into HttpException::setTitle() and setDescription() and using static, plain-text error copy instead.
They should also register a custom error renderer (an ErrorRendererInterface implementation, or a subclass of HtmlErrorRenderer that escapes the title and description) for the HTML media type.

Weakness: CWE-79 (Improper Neutralization of Input During Web Page Generation)

## Which versions are affected by CVE-2026-48157?

2 open source packages ship an affected version, including slim/slim.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `slim/slim` | Packagist | From 4.4.0 | 4.15.2 |
| `slim/slim` | Packagist | From 4.4.0 | 4.15.2 |

## How do I fix CVE-2026-48157?

Upgrade slim/slim to 4.15.2 or later.

## Is CVE-2026-48157 being exploited?

There is no known exploitation of CVE-2026-48157 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-48157 and fix it if it is affected.

What it is: CVE-2026-48157 is a medium-severity cross-site scripting vulnerability in slimphp Slim, published on 15 Jun 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.
Exploitation: There is no known exploitation of CVE-2026-48157 in the wild and no public exploit code.

Affected packages and fixed versions:
- slim/slim (Packagist): affected from 4.4.0; fixed in 4.15.2
- slim/slim (Packagist): affected from 4.4.0; fixed in 4.15.2

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-48157/ (Markdown: https://insights.sbomify.com/CVE-2026-48157/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-48157
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-48157
- OSV: https://osv.dev/vulnerability/CVE-2026-48157

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-48157/
Summaries are generated and may contain mistakes; the official description above is the record.