Slim has Reflected XSS in the HtmlErrorRenderer

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

6.1 · CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N

EPSS

• CVE-2026-48157: 0.17% estimated exploitation activity in the next 30 days; percentile 5.99 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

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…

Published by the source

23 Jun 2026, 21:54 UTC

Last modified by the source

23 Jun 2026, 21:54 UTC

Source last checked

26 Oct 2026, 14:49 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-53h4-8rc4-f539

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# Patch Next advisory brief: CVE-2026-48157

Advisory: Slim has Reflected XSS in the HtmlErrorRenderer
IDs: CVE-2026-48157, GHSA-53h4-8rc4-f539
Record: https://patchnext.com/advisories/cve-2026-48157 (revision 1, source checked 26 Oct 2026, 14:49 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Medium (CVSS 6.1)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: slim/slim 4.15.2. A vendor fix does not mean a deployment is fixed.

## Affected components
- Packagist slim/slim: affected >= 4.4.0, <= 4.15.1; fixed in 4.15.2

## Suggested inspection (read-only)
- Packagist slim/slim: check the installed version with your package manager.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on slim/slim.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-53h4-8rc4-f539 (GitHub-reviewed advisory GHSA-53h4-8rc4-f539 lists affected ranges: Packagist slim/slim >=4.4.0 <=4.15.1)

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