{"items":[{"id":"NVI-00016199","kind":"vulnerability","title":"Caddy: FastCGI header normalization bypass in `forward_auth copy_headers`","revision":2,"unknowns":["Customer inventory, deployment, reachability and exploitation have not been inspected.","NVD lastModified does not establish freshness of every associated CPE record."],"lifecycle":"active","identifiers":["GHSA-f59h-q822-g45g","CVE-2026-52845"],"plain_summary":"GitHub lists this reviewed advisory for github.com/caddyserver/caddy/v2, github.com/caddyserver/caddy. Published version ranges and source prerequisites are shown below; this is not an inspection of a visitor’s application.","review_status":"source_listed","control_topics":[],"public_actions":[{"summary":"Identify the exact component and deployed version, examine the linked publisher’s conditions, and retain evidence of any mitigation.","source_ids":["sr-5faa1df583f26a59a360c818a28cb9b9"],"action_type":"investigate","limitations":"Confirm current vendor support, compatibility and deployment evidence. This report has not tested a fix in your system.","current_supported_target":null}],"schema_version":"1.1.0","source_metrics":[{"kind":"CVSS","as_of":"2026-07-24T13:26:47.000Z","value":"8.1 high","meaning":"GitHub source severity; exploitability and local consequence require separate evidence.","source_id":"sr-43e659f5712fb6f601b66aba16eb1626"},{"kind":"CVSS","as_of":"2026-10-25T23:10:00.167Z","value":"8.1 HIGH (3.1)","meaning":"security-advisories@github.com severity; no combined Null risk score.","source_id":"sr-5faa1df583f26a59a360c818a28cb9b9"},{"kind":"CVSS","as_of":"2026-10-25T23:10:00.167Z","value":"8.1 HIGH (3.1)","meaning":"0b0ca135-0b70-47e7-9f44-1890c2a1c46c severity; no combined Null risk score.","source_id":"sr-5faa1df583f26a59a360c818a28cb9b9"}],"why_it_matters":"Published affected context helps an owner decide what evidence to gather. This report has not examined your application.","related_sources":[{"id":"sr-43e659f5712fb6f601b66aba16eb1626","url":"https://github.com/advisories/GHSA-f59h-q822-g45g","basis":"vendor_advisory","notes":"GitHub Advisory Database; CC-BY-4.0. Each advisory links its original attribution. Null normalizes fields.","title":"GHSA-f59h-q822-g45g","publisher":"GitHub Advisory Database","observed_at":"2026-11-03T17:42:43.803Z"},{"id":"sr-5faa1df583f26a59a360c818a28cb9b9","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-52845","basis":"official_catalog","notes":"This product uses data from the NVD API but is not endorsed or certified by the NVD.","title":"CVE-2026-52845","publisher":"NIST National Vulnerability Database","observed_at":"2026-11-08T01:47:57.993Z"}],"affected_context":[{"certainty":"source_listed","source_ids":["sr-43e659f5712fb6f601b66aba16eb1626"],"technology":"github.com/caddyserver/caddy/v2","known_exclusions":[],"conditions_summary":"### Summary\n\n`forward_auth copy_headers` deletes the exact client-supplied identity header before copying the trusted value from the auth gateway. But when the request later goes through `php_fastcgi`, Caddy normalizes HTTP headers into CGI variables by replacing `-` with `_`.\n\nThis lets a client send an underscore alias that survives the `forward_auth` delete step but becomes the same PHP/FastCGI variable:\n\n```text\nRemote-Groups  -> HTTP_REMOTE_GROUPS\nRemote_Groups  -> HTTP_REMOTE_GROUPS\n\nRemote-User    -> HTTP_REMOTE_USER\nRemote_User    -> HTTP_REMOTE_USER\n```\n\nResult: a remote client can inject or sometimes override identity/group headers trusted by PHP/FastCGI applications behind Caddy.\n\n### Details\n\n`forward_auth copy_headers` intentionally removes client-controlled headers before setting values from the auth response:\n\n- `modules/caddyhttp/reverseproxy/forwardauth/caddyfile.go:212`\n- `modules/caddyhttp/reverseproxy/forwardauth/caddyfile.go:222`\n\nThat delete is exact-field deletion through `http.Header.Del()`:\n\n- `modules/caddyhttp/headers/headers.go:255`\n- `modules/caddyhttp/headers/headers.go:281`\n\nSo deleting `Remote-Groups` does not delete `Remote_Groups`.\n\nLater, FastCGI ","public_affected_ranges":["< 2.11.4"]},{"certainty":"source_listed","source_ids":["sr-43e659f5712fb6f601b66aba16eb1626"],"technology":"github.com/caddyserver/caddy","known_exclusions":[],"conditions_summary":"### Summary\n\n`forward_auth copy_headers` deletes the exact client-supplied identity header before copying the trusted value from the auth gateway. But when the request later goes through `php_fastcgi`, Caddy normalizes HTTP headers into CGI variables by replacing `-` with `_`.\n\nThis lets a client send an underscore alias that survives the `forward_auth` delete step but becomes the same PHP/FastCGI variable:\n\n```text\nRemote-Groups  -> HTTP_REMOTE_GROUPS\nRemote_Groups  -> HTTP_REMOTE_GROUPS\n\nRemote-User    -> HTTP_REMOTE_USER\nRemote_User    -> HTTP_REMOTE_USER\n```\n\nResult: a remote client can inject or sometimes override identity/group headers trusted by PHP/FastCGI applications behind Caddy.\n\n### Details\n\n`forward_auth copy_headers` intentionally removes client-controlled headers before setting values from the auth response:\n\n- `modules/caddyhttp/reverseproxy/forwardauth/caddyfile.go:212`\n- `modules/caddyhttp/reverseproxy/forwardauth/caddyfile.go:222`\n\nThat delete is exact-field deletion through `http.Header.Del()`:\n\n- `modules/caddyhttp/headers/headers.go:255`\n- `modules/caddyhttp/headers/headers.go:281`\n\nSo deleting `Remote-Groups` does not delete `Remote_Groups`.\n\nLater, FastCGI ","public_affected_ranges":["<= 1.0.5"]}],"null_published_at":"2026-11-08T19:53:44.061Z","source_updated_at":"2026-07-24T13:26:47.000Z","source_disclosed_at":"2026-06-16T21:28:28.000Z","is_synthetic_fixture":false,"null_last_reviewed_at":null,"public_change_summary":"Source facts changed; compare the preserved prior revision.","null_first_observed_at":"2026-11-03T17:42:43.803Z"},{"id":"NVI-00016199","kind":"vulnerability","title":"Caddy: FastCGI header normalization bypass in `forward_auth copy_headers`","revision":1,"unknowns":["Customer inventory, deployment, reachability and exploitation have not been inspected."],"lifecycle":"active","identifiers":["GHSA-f59h-q822-g45g","CVE-2026-52845"],"plain_summary":"GitHub lists this reviewed advisory for github.com/caddyserver/caddy/v2, github.com/caddyserver/caddy. Published version ranges and source prerequisites are shown below; this is not an inspection of a visitor’s application.","review_status":"source_listed","control_topics":[],"public_actions":[{"summary":"Identify the exact component and deployed version, examine the linked publisher’s conditions, and retain evidence of any mitigation.","source_ids":["sr-43e659f5712fb6f601b66aba16eb1626"],"action_type":"investigate","limitations":"Confirm current vendor support, compatibility and deployment evidence. This report has not tested a fix in your system.","current_supported_target":null}],"schema_version":"1.1.0","source_metrics":[{"kind":"CVSS","as_of":"2026-07-24T13:26:47.000Z","value":"8.1 high","meaning":"GitHub source severity; exploitability and local consequence require separate evidence.","source_id":"sr-43e659f5712fb6f601b66aba16eb1626"}],"why_it_matters":"Published affected context helps an owner decide what evidence to gather. This report has not examined your application.","related_sources":[{"id":"sr-43e659f5712fb6f601b66aba16eb1626","url":"https://github.com/advisories/GHSA-f59h-q822-g45g","basis":"vendor_advisory","notes":"GitHub Advisory Database; CC-BY-4.0. Each advisory links its original attribution. Null normalizes fields.","title":"GHSA-f59h-q822-g45g","publisher":"GitHub Advisory Database","observed_at":"2026-11-03T17:42:43.803Z"}],"affected_context":[{"certainty":"source_listed","source_ids":["sr-43e659f5712fb6f601b66aba16eb1626"],"technology":"github.com/caddyserver/caddy/v2","known_exclusions":[],"conditions_summary":"### Summary\n\n`forward_auth copy_headers` deletes the exact client-supplied identity header before copying the trusted value from the auth gateway. But when the request later goes through `php_fastcgi`, Caddy normalizes HTTP headers into CGI variables by replacing `-` with `_`.\n\nThis lets a client send an underscore alias that survives the `forward_auth` delete step but becomes the same PHP/FastCGI variable:\n\n```text\nRemote-Groups  -> HTTP_REMOTE_GROUPS\nRemote_Groups  -> HTTP_REMOTE_GROUPS\n\nRemote-User    -> HTTP_REMOTE_USER\nRemote_User    -> HTTP_REMOTE_USER\n```\n\nResult: a remote client can inject or sometimes override identity/group headers trusted by PHP/FastCGI applications behind Caddy.\n\n### Details\n\n`forward_auth copy_headers` intentionally removes client-controlled headers before setting values from the auth response:\n\n- `modules/caddyhttp/reverseproxy/forwardauth/caddyfile.go:212`\n- `modules/caddyhttp/reverseproxy/forwardauth/caddyfile.go:222`\n\nThat delete is exact-field deletion through `http.Header.Del()`:\n\n- `modules/caddyhttp/headers/headers.go:255`\n- `modules/caddyhttp/headers/headers.go:281`\n\nSo deleting `Remote-Groups` does not delete `Remote_Groups`.\n\nLater, FastCGI ","public_affected_ranges":["< 2.11.4"]},{"certainty":"source_listed","source_ids":["sr-43e659f5712fb6f601b66aba16eb1626"],"technology":"github.com/caddyserver/caddy","known_exclusions":[],"conditions_summary":"### Summary\n\n`forward_auth copy_headers` deletes the exact client-supplied identity header before copying the trusted value from the auth gateway. But when the request later goes through `php_fastcgi`, Caddy normalizes HTTP headers into CGI variables by replacing `-` with `_`.\n\nThis lets a client send an underscore alias that survives the `forward_auth` delete step but becomes the same PHP/FastCGI variable:\n\n```text\nRemote-Groups  -> HTTP_REMOTE_GROUPS\nRemote_Groups  -> HTTP_REMOTE_GROUPS\n\nRemote-User    -> HTTP_REMOTE_USER\nRemote_User    -> HTTP_REMOTE_USER\n```\n\nResult: a remote client can inject or sometimes override identity/group headers trusted by PHP/FastCGI applications behind Caddy.\n\n### Details\n\n`forward_auth copy_headers` intentionally removes client-controlled headers before setting values from the auth response:\n\n- `modules/caddyhttp/reverseproxy/forwardauth/caddyfile.go:212`\n- `modules/caddyhttp/reverseproxy/forwardauth/caddyfile.go:222`\n\nThat delete is exact-field deletion through `http.Header.Del()`:\n\n- `modules/caddyhttp/headers/headers.go:255`\n- `modules/caddyhttp/headers/headers.go:281`\n\nSo deleting `Remote-Groups` does not delete `Remote_Groups`.\n\nLater, FastCGI ","public_affected_ranges":["<= 1.0.5"]}],"null_published_at":"2026-11-04T10:04:27.904Z","source_updated_at":"2026-07-24T13:26:47.000Z","source_disclosed_at":"2026-06-16T21:28:28.000Z","is_synthetic_fixture":false,"null_last_reviewed_at":null,"public_change_summary":"First indexed by Null; source disclosure date is shown separately.","null_first_observed_at":"2026-11-03T17:42:43.803Z"}],"next_cursor":null,"snapshot_revision":"42594"}