CVE-2026-57210 Heimdall: IP Spoofing via Unvalidated Forwarding Headers
- Exploited in the wild
- Not known
- Fix
- Available
What is CVE-2026-57210?
CVE-2026-57210 is a high-severity vulnerability in dadrus heimdall, published on 23 Oct 2026.
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.
Which versions are affected by CVE-2026-57210?
3 open source packages ship an affected version, including https://github.com/dadrus/heimdall and github.com/dadrus/heimdall.
| Package | Affected | Fixed in |
|---|---|---|
https://github.com/dadrus/heimdall Go | All versions | 0.17.17 |
https://github.com/dadrus/heimdall Go | All versions | 0.17.17 |
github.com/dadrus/heimdall Go | All versions | 0.17.17 |
How do I fix CVE-2026-57210?
Upgrade https://github.com/dadrus/heimdall to 0.17.17 or later.
Is CVE-2026-57210 being exploited?
There is no known exploitation of CVE-2026-57210 in the wild and no public exploit code.
Sources
Also known as GHSA-38x9-25wx-7fg2, GO-2026-5075.