Vulnerability · Published Oct 23, 2026 · Assigned by GitHub_M
CVE-2026-57209Heimdall: Forwarded Header Injection via Unsanitized Host Header in Proxy Mode
High 7.0
In plain English
A high-severity improper input validation in heimdall from dadrus. Proof-of-concept exploit code is public. The chance it is exploited in the next 30 days is estimated at 0.5% (higher than 42% 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 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 packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| Go | github.com/dadrus/heimdall | 0.17.17 | GHSA-4jgr-pg2m-m988 |
| Go | github.com/dadrus/heimdall | 0.17.17 | GO-2026-5125 |
Affected products (as reported)
Weakness: CWE-20, CWE-74 · 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-4jgr-pg2m-m988 x_refsource_CONFIRM
- https://github.com/dadrus/heimdall/releases/tag/v0.17.17 x_refsource_MISC