Vulnerability · Published Oct 23, 2026 · Assigned by GitHub_M
CVE-2026-57210Heimdall: IP Spoofing via Unvalidated Forwarding Headers
High 7.0
In plain English
A high-severity improper input validation in heimdall from dadrus. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.3% (higher than 24% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.
Official 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.
Affected packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| Go | github.com/dadrus/heimdall | 0.17.17 | GO-2026-5075 |
| Go | https://github.com/dadrus/heimdall | 0.17.17 | GHSA-38x9-25wx-7fg2 |
Affected products (as reported)
Weakness: CWE-20, CWE-116, CWE-290 · 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
References
- https://github.com/dadrus/heimdall/security/advisories/GHSA-38x9-25wx-7fg2 x_refsource_CONFIRM
- https://github.com/dadrus/heimdall/releases/tag/v0.17.17 x_refsource_MISC