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Vulnerability · Published Sep 15, 2026 · Assigned by GitHub_M

CVE-2026-69216Http4s: Ember chunk parser lenience (TE.TE request smuggling)

Medium 5.4

In plain English

A medium-severity security flaw in http4s from http4s. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.4% (higher than 31% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.

Severity (CVSS 3.1)5.4Medium
Exploit odds (30 days)0.4%top 69.2% of all CVEs
Exploited in the wildNo reportsCISA SSVC: none
Attack toolingNoneno public tooling known

Official description

Http4s is a Scala interface for HTTP services. Prior to 0.23.35 and 1.0.0-M47, Ember’s chunk decoder trims the chunk-size token and accepts leading plus or minus signs instead of requiring one or more hexadecimal digits followed by the required CRLF. When an intermediary forwards chunked data without re-encoding and interprets malformed chunk boundaries differently, an unauthenticated attacker can create TE.TE request smuggling that bypasses intermediary controls, poisons caches, or hijacks the request queue. The same response-path leniency can enable response smuggling against an ember-client used as a gateway when the upstream is malicious or compromised. This issue is fixed in versions 0.23.35 and 1.0.0-M47.

Affected packages & fixed versions

EcosystemPackageFixed inAdvisory
Mavenorg.http4s:http4s-ember-core_2.120.23.35GHSA-jrpm-956j-96jg
Mavenorg.http4s:http4s-ember-core_2.130.23.35GHSA-jrpm-956j-96jg
Mavenorg.http4s:http4s-ember-core_2.131.0.0-M47GHSA-jrpm-956j-96jg
Mavenorg.http4s:http4s-ember-core_30.23.35GHSA-jrpm-956j-96jg
Mavenorg.http4s:http4s-ember-core_31.0.0-M47GHSA-jrpm-956j-96jg

Affected products (as reported)

VendorProductVersions
http4s http4s < 0.23.35>= 1.0.0-M1, < 1.0.0-M47

Weakness: CWE-444 · Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:L/I:L/A:N

References