Heimdall: IP Spoofing via Unvalidated Forwarding Headers in github.com/dadrus/heimdall

Exploitation

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

CVSS 4.0

7.0 · 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 · score source

EPSS

• CVE-2026-57210: 0.31% estimated exploitation activity in the next 30 days; percentile 23.55 (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.

When the trusted_proxies option is configured, heimdall extracts client IP addresses from the Forwarded and X-Forwarded-For headers and exposes them as Request.ClientIPAddresses to the rule pipeline. However, extracted values are not validated to be syntactically valid IP addresses. Arbitrary strings, malformed IP literals, and RFC 7239 unknown values and obfuscated identifiers are accepted without further checks. In addition, the Forwarded header parser splits on commas and semicolons without accounting for RFC 7239 quoted strings, which can cause a single quoted value to be parsed as multiple entries, with fragments treated as independent addresses. Request.ClientIPAddresses is available to all pipeline mechanisms. Its contents can therefore influence rule evaluation in deployments where rules reference this property. Additionally, in proxy mode, Request.ClientIPAddresses is used directly to construct the X-Forwarded-For and Forwarded headers forwarded to upstream services.…

Published by the source

11 Aug 2026, 20:19 UTC

Last modified by the source

11 Aug 2026, 20:33 UTC

Source last checked

25 Oct 2026, 04:53 UTC

1. Revision 2 · amended · 25 Oct 2026

   Reviewed OSV alias/range/CVSS4 correction; package source scopes and original publication preserved. No customer finding resolved.

2. Revision 1 · created · 24 Oct 2026

   Published from osv record GO-2026-5075

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# Patch Next advisory brief: CVE-2026-57210

Advisory: Heimdall: IP Spoofing via Unvalidated Forwarding Headers in github.com/dadrus/heimdall
IDs: CVE-2026-57210, GHSA-38x9-25wx-7fg2
Record: https://patchnext.com/advisories/cve-2026-57210 (revision 2, source checked 25 Oct 2026, 04:53 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: High (CVSS 7.0)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: github.com/dadrus/heimdall 0.17.17. A vendor fix does not mean a deployment is fixed.

## Affected components
- Go github.com/dadrus/heimdall: affected < 0.17.17; fixed in 0.17.17

## Suggested inspection (read-only)
- Go github.com/dadrus/heimdall: 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 github.com/dadrus/heimdall.
- 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://osv.dev/vulnerability/GO-2026-5075 (OSV record GO-2026-5075 lists affected ranges: Go github.com/dadrus/heimdall >=0 <0.17.17 (fixed))

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