---
id: CVE-2026-57209
title: 'Heimdall: Forwarded Header Injection via Unsanitized Host Header in Proxy Mode'
summary: >-
  Heimdall is a cloud native Identity Aware Proxy and Access Control Decision
  service. Prior to version 0.17.17, when Heimdall operates in proxy mode, it
  constructs the Forwarded HTTP header after executing the matched rule pipeline
  by ins…
severity: high
cvss: 7
cvssVector: 'CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:N/SC:H/SI:H/SA:N'
cvssSource: cna
cwe:
  - CWE-20
  - CWE-74
vendor: dadrus
product: heimdall
affected:
  - heimdall < 0.17.17
ssvc:
  exploitation: poc
  automatable: 'yes'
  technicalImpact: partial
  timestamp: '2026-10-29T13:15:43.399575Z'
exploitAvailable: true
published: '2026-10-23'
updated: '2026-10-29'
sourceUpdated: '2026-10-29T13:16:52.579Z'
source: CVEORG
sourceUrl: 'https://www.cve.org/CVERecord?id=CVE-2026-57209'
references:
  - url: 'https://github.com/dadrus/heimdall/security/advisories/GHSA-4jgr-pg2m-m988'
    label: 'https://github.com/dadrus/heimdall/security/advisories/GHSA-4jgr-pg2m-m988'
  - url: 'https://github.com/dadrus/heimdall/releases/tag/v0.17.17'
    label: 'https://github.com/dadrus/heimdall/releases/tag/v0.17.17'
  - url: 'https://github.com/dadrus/heimdall'
tags:
  - cve.org
  - exploit-available
  - osv
  - go
epss: 0.00488
epssPercentile: 0.4204
aliases:
  - GHSA-4jgr-pg2m-m988
  - GO-2026-5125
ecosystem: go
patched:
  - github.com/dadrus/heimdall 0.17.17
ingestedAt: '2026-07-21T19:04:58.077Z'
---

## Overview

Heimdall is a cloud native Identity Aware Proxy and Access Control Decision service. Prior to version 0.17.17, when Heimdall operates in proxy mode, it constructs the Forwarded HTTP header after executing the matched rule pipeline by inserting the incoming request's Host header value directly into the header string without sanitizing commas or semicolons. This allows an attacker to inject additional parameters into the Forwarded header, potentially spoofing IP addresses for upstream services. This issue has been patched in version 0.17.17.

## Affected

- `heimdall < 0.17.17`

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.

## Package advisory (CVE-2026-57209)

Affected packages:

- `github.com/dadrus/heimdall < 0.17.17`

Patched in:

- `github.com/dadrus/heimdall 0.17.17`

Source: https://osv.dev/vulnerability/GHSA-4jgr-pg2m-m988