CVE-2021-23339: HTTP Request Smuggling

Severity: medium (CVSS 6.5 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.7% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2021-02-17 · updated 2026-06-17
Weakness: CWE-444

Description

This affects all versions before 10.1.14 and from 10.2.0 to 10.2.4 of package com.typesafe.akka:akka-http-core. It allows multiple Transfer-Encoding headers.

Affected products

com.typesafe.akka:akka-http-core: before 10.1.14; from 10.2.0 before 10.2.4 — fixed in 10.1.14, 10.2.4

How to fix

Upgrade to a fixed version: com.typesafe.akka:akka-http-core 10.1.14, 10.2.4. Check the vendor advisory for mitigations.

References

https://github.com/akka/akka-http/pull/3754%23issuecomment-779265201
https://snyk.io/vuln/SNYK-JAVA-COMTYPESAFEAKKA-1075043
https://github.com/akka/akka-http/pull/3754%23issuecomment-779265201
https://snyk.io/vuln/SNYK-JAVA-COMTYPESAFEAKKA-1075043

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