Kirby: Request header injection in Http\Remote

Exploitation

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

CVSS 4.0

6.9 · CVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:N/VC:N/VI:N/VA:N/SC:N/SI:H/SA:N · score source

EPSS

• CVE-2026-50188: 0.44% estimated exploitation activity in the next 30 days; percentile 38.56 (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.

TL;DR This vulnerability affects Kirby sites and plugins that use the Kirby\Http\Remote class (including Remote::request(), Remote::get(), Remote::post(), and similar helpers) to send outgoing HTTP requests and that pass untrusted, user-controlled data into the headers option of such a request. By including newline characters in the value of the header, it was possible to inject a separate, independent header that was not intended to be set. A successful attack requires that an application or plugin forwards attacker-influenced input into a request header value. Sites that only send static, developer-defined headers are not affected. The attack does not target Panel users or site visitors directly; it targets the remote service that Kirby connects to. In Kirby's default configuration, the Remote class is not exposed to untrusted input, so a default installation is not affected. The vulnerability becomes relevant for custom code, plugins, or integrations that build request headers…

Published by the source

18 Jun 2026, 15:04 UTC

Last modified by the source

18 Jun 2026, 15:04 UTC

Source last checked

26 Oct 2026, 14:49 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-4v4h-m2qq-ppgw

Preview the exact text before you copy it. Commands are read-only suggestions; review them before running anything.

# Patch Next advisory brief: CVE-2026-50188

Advisory: Kirby: Request header injection in `Http\Remote`
IDs: CVE-2026-50188, GHSA-4v4h-m2qq-ppgw
Record: https://patchnext.com/advisories/cve-2026-50188 (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 6.9)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: getkirby/cms 5.4.4, 4.9.4. A vendor fix does not mean a deployment is fixed.

## Affected components
- Packagist getkirby/cms: affected <= 4.9.3; >= 5.0.0-alpha.1, <= 5.4.3; fixed in 4.9.4, 5.4.4

## Suggested inspection (read-only)
- Packagist getkirby/cms: 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 getkirby/cms.
- 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-4v4h-m2qq-ppgw (GitHub-reviewed advisory GHSA-4v4h-m2qq-ppgw lists affected ranges: Packagist getkirby/cms >=0 =5.0.0-alpha.1 <=5.4.3)

Commands are suggestions: review each one before running it.