{"cve":"CVE-2026-73495","nvd":{"published":"2026-08-12T22:17:16.820","modified":"2026-10-24T15:10:00.190","status":"Deferred","description":"blaze is a Scala library for building asynchronous pipelines, with a focus on network IO. Prior to 0.23.18 and 1.0.0-M42, blaze-server can merge HTTP/1.1 chunked-body trailer fields into Request.headers. Because trailer fields are attacker-controlled, an unauthenticated remote client can inject arbitrary header names and values, including X-Forwarded-For and internal authorization headers, that a fronting proxy sanitized from the request-header section, bypassing header-based trust decisions in the application. Any http4s application using BlazeServerBuilder over HTTP/1.1 whose routes or middleware trust proxy-set headers, including X-Forwarded-For, X-Real-IP, and X-Forwarded-Host, is affected. If a fronting proxy strips or normalizes those headers but forwards chunked bodies with trailers intact, an attacker can spoof client IP for allow-lists, rate limits, or auditing, forge the https scheme, or inject internal authorization headers. A promoted Connection: close trailer is also honored, allowing attacker-controlled termination of pooled backend connections. This issue is fixed in versions 0.23.18 and 1.0.0-M42.","cvss_v4":null,"cvss_v3":{"version":"3.1","vector":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N","score":7.4},"cwes":["CWE-444"],"references":["https://github.com/http4s/blaze/commit/ef3e666c146cfc16cb6603f1fc3c464daab4a24f","https://github.com/http4s/blaze/releases/tag/v0.23.18","https://github.com/http4s/blaze/releases/tag/v1.0.0-M42","https://github.com/http4s/blaze/security/advisories/GHSA-46q4-43ph-c6fr"],"products":[],"source":"nvd","synced_at":"2026-10-24T16:53:35.584907681+00:00"},"epss":{"cve":"CVE-2026-73495","score":0.0048,"percentile":0.41099,"date":"2026-10-25"},"kev":null,"osv":[{"id":"GHSA-46q4-43ph-c6fr","url":"https://osv.dev/vulnerability/GHSA-46q4-43ph-c6fr","summary":"blaze: Chunked-body trailer fields promoted into Request.headers in blaze-server (front-end header-sanitization bypass)","modified":"2026-08-12T21:25:59.135045Z","packages":[{"ecosystem":"Maven","name":"org.http4s:blaze-http_2.13","purl":"pkg:maven/org.http4s/blaze-http_2.13","ranges":["<0.23.18"],"fixed":["0.23.18"]},{"ecosystem":"Maven","name":"org.http4s:blaze-http_2.12","purl":"pkg:maven/org.http4s/blaze-http_2.12","ranges":["<0.23.18"],"fixed":["0.23.18"]},{"ecosystem":"Maven","name":"org.http4s:blaze-http_3","purl":"pkg:maven/org.http4s/blaze-http_3","ranges":["<0.23.18"],"fixed":["0.23.18"]},{"ecosystem":"Maven","name":"org.http4s:blaze-http_3","purl":"pkg:maven/org.http4s/blaze-http_3","ranges":[">=1.0.0-M1 <1.0.0-M42"],"fixed":["1.0.0-M42"]},{"ecosystem":"Maven","name":"org.http4s:blaze-http_2.13","purl":"pkg:maven/org.http4s/blaze-http_2.13","ranges":[">=1.0.0-M1 <1.0.0-M42"],"fixed":["1.0.0-M42"]}]}],"attribution":["This product uses the NVD API but is not endorsed or certified by the NVD.","EPSS scores: FIRST Exploit Prediction Scoring System, https://www.first.org/epss","Known exploited vulnerabilities: CISA Known Exploited Vulnerabilities Catalog, https://www.cisa.gov/known-exploited-vulnerabilities-catalog","Package advisories: OSV (https://osv.dev), from the GitHub Advisory Database, PyPA, Go, RustSec and other ecosystem databases, under CC-BY 4.0 or CC0","CVE records: the CVE Program's CVE List (https://www.cve.org), under its terms of use (https://www.cve.org/Legal/TermsOfUse). CVE is a registered trademark of The MITRE Corporation; this product is not affiliated with the CVE Program."]}