{"id":"CVE-2026-73495","title":"blaze is a Scala library for building asynchronous pipelines, with a focus on network IO","summary":"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 attack…","severity":"high","cvss":7.4,"cvssVector":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N","cwe":["CWE-444"],"vendor":"http4s","product":"blaze","affected":["blaze < 0.23.18","blaze >= 1.0.0-M1, < 1.0.0-M42"],"published":"2026-08-12","updated":"2026-09-09","sourceUpdated":"2026-09-09T21:02:22.660","source":"NVD","sourceUrl":"https://nvd.nist.gov/vuln/detail/CVE-2026-73495","references":[{"url":"https://github.com/http4s/blaze/commit/ef3e666c146cfc16cb6603f1fc3c464daab4a24f","label":"security-advisories@github.com"},{"url":"https://github.com/http4s/blaze/releases/tag/v0.23.18","label":"security-advisories@github.com"},{"url":"https://github.com/http4s/blaze/releases/tag/v1.0.0-M42","label":"security-advisories@github.com"},{"url":"https://github.com/http4s/blaze/security/advisories/GHSA-46q4-43ph-c6fr","label":"security-advisories@github.com"}],"tags":["nvd","cve.org"],"ssvc":{"exploitation":"none","automatable":"no","technicalImpact":"total","timestamp":"2026-08-13T13:02:55.958244Z"},"ingestedAt":"2026-09-10T19:07:15.840Z","epss":0.00289,"epssPercentile":0.21766,"slug":"CVE-2026-73495","body":"## Overview\n\nblaze 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.\n\n## Remediation\n\nRefer to the linked advisories for vendor-supplied fixes and affected version ranges.","depth":"twilight","depthScore":41,"depthScoreParts":{"impact":40.7,"likelihood":0.1,"exploitation":0,"ransomware":0},"changes":[]}