Description
Heimdall is a cloud native Identity Aware Proxy and Access Control Decision service. Prior to version 0.17.17, when the trusted_proxies option is configured, heimdall extracts client IP addresses from the Forwarded (for= parameter) 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 , and ; without accounting for RFC 7239 quoted strings, which can cause a single quoted value to be parsed as multiple entries, with fragments — including trailing quote characters — treated as independent addresses. This issue has been patched in version 0.17.17.
Published: 2026-10-23
Score: 7 High
EPSS: n/a
KEV: No
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Remediation

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Tracking

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Advisories
Source ID Title
Github GHSA Github GHSA GHSA-38x9-25wx-7fg2 Heimdall: IP Spoofing via Unvalidated Forwarding Headers
History

Fri, 23 Oct 2026 12:45:00 +0000

Type Values Removed Values Added
Description Heimdall is a cloud native Identity Aware Proxy and Access Control Decision service. Prior to version 0.17.17, when the trusted_proxies option is configured, heimdall extracts client IP addresses from the Forwarded (for= parameter) 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 , and ; without accounting for RFC 7239 quoted strings, which can cause a single quoted value to be parsed as multiple entries, with fragments — including trailing quote characters — treated as independent addresses. This issue has been patched in version 0.17.17.
Title Heimdall: IP Spoofing via Unvalidated Forwarding Headers
Weaknesses CWE-116
CWE-20
CWE-290
References
Metrics cvssV4_0

{'score': 7, 'vector': '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'}

Subscriptions

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cve-icon MITRE

Status: PUBLISHED

Assigner: GitHub_M

Published:

Updated: 2026-10-23T12:28:09.427Z

Reserved: 2026-06-24T02:00:46.801Z

Link: CVE-2026-57210

cve-icon Vulnrichment

No data.

cve-icon NVD

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cve-icon Redhat

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cve-icon OpenCVE Enrichment

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Weaknesses
  • CWE-116

    Improper Encoding or Escaping of Output

  • CWE-20

    Improper Input Validation

  • CWE-290

    Authentication Bypass by Spoofing