Description
blaze is a Scala library for building asynchronous pipelines, with a focus on network IO. Prior to 0.23.18 and from 1.0.0-M1 until 1.0.0-M42, five HTTP/1.1 conformance laxities in the hand-written Java parser under http/src/main/java/org/http4s/blaze/http/parser/ can cause blaze to derive a different request boundary than a stricter fronting intermediary. A default BlazeServerBuilder accepts invalid or valueless header field names that violate tchar syntax, obsolete folded field lines (obs-fold), unsupported Transfer-Encoding values, duplicate Content-Length fields, and requests containing both Transfer-Encoding and Content-Length. If a lenient or legacy proxy forwards the malformed bytes but interprets them differently, the disagreement can permit front-end authorization bypass, response-queue poisoning on pooled backend connections, or cache poisoning. Exploitation requires a pair of disagreeing parsers; no non-default blaze configuration is required. The affected checks are enforced in BodyAndHeaderParser and Http1ServerParser. This issue is fixed in versions 0.23.18 and 1.0.0-M42.
Published: 2026-09-14
Score: 7.4 High
EPSS: n/a
KEV: No
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Remediation

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Tracking

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Advisories
Source ID Title
Github GHSA Github GHSA GHSA-mhvj-jhpq-885v blaze: Multiple HTTP/1.1 request-smuggling primitives in blaze's Java wire parser
History

Mon, 14 Sep 2026 21:30:00 +0000

Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'no', 'Exploitation': 'none', 'Technical Impact': 'total'}, 'version': '2.0.3'}


Mon, 14 Sep 2026 21:00:00 +0000

Type Values Removed Values Added
Description blaze is a Scala library for building asynchronous pipelines, with a focus on network IO. Prior to 0.23.18 and from 1.0.0-M1 until 1.0.0-M42, five HTTP/1.1 conformance laxities in the hand-written Java parser under http/src/main/java/org/http4s/blaze/http/parser/ can cause blaze to derive a different request boundary than a stricter fronting intermediary. A default BlazeServerBuilder accepts invalid or valueless header field names that violate tchar syntax, obsolete folded field lines (obs-fold), unsupported Transfer-Encoding values, duplicate Content-Length fields, and requests containing both Transfer-Encoding and Content-Length. If a lenient or legacy proxy forwards the malformed bytes but interprets them differently, the disagreement can permit front-end authorization bypass, response-queue poisoning on pooled backend connections, or cache poisoning. Exploitation requires a pair of disagreeing parsers; no non-default blaze configuration is required. The affected checks are enforced in BodyAndHeaderParser and Http1ServerParser. This issue is fixed in versions 0.23.18 and 1.0.0-M42.
Title blaze: Multiple HTTP/1.1 request-smuggling primitives in blaze's Java wire parser
Weaknesses CWE-444
References
Metrics cvssV3_1

{'score': 7.4, 'vector': 'CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N'}


Subscriptions

No data.

cve-icon MITRE

Status: PUBLISHED

Assigner: GitHub_M

Published:

Updated: 2026-09-14T20:05:52.181Z

Reserved: 2026-08-12T19:00:33.735Z

Link: CVE-2026-73494

cve-icon Vulnrichment

Updated: 2026-09-14T19:21:22.363Z

cve-icon NVD

Status : Received

Published: 2026-09-14T18:19:58.857

Modified: 2026-09-14T20:16:50.707

Link: CVE-2026-73494

cve-icon Redhat

No data.

cve-icon OpenCVE Enrichment

No data.

Weaknesses