CVE-2026-23941: Request smuggling via first-wins Content-Length parsing in inets httpd
Inconsistent Interpretation of HTTP Requests ('HTTP Request Smuggling') vulnerability in Erlang OTP (inets httpd module) allows HTTP Request Smuggling. This vulnerability is associated with program files lib/inets/src/http_server/httpd_request.erl and program routines httpd_request:parse_headers/7. The server does not reject or normalize duplicate Content-Length headers. The earliest Content-Length in the request is used for body parsing while common reverse proxies (nginx, Apache httpd, Envoy) honor the last Content-Length value. This violates RFC 9112 Section 6.3 and allows front-end/back-end desynchronization, leaving attacker-controlled bytes queued as the start of the next request. This issue affects OTP from OTP 17.0 until OTP 28.4.1, OTP 27.3.4.9 and OTP 26.2.5.18, corresponding to inets from 5.10 until 9.6.1, 9.3.2.3 and 9.1.0.5.
Affected Software
Remediation
Event History
Frequently Asked Questions
What is the severity of CVE-2026-23941?
CVE-2026-23941 is classified as a high-severity vulnerability due to its potential for HTTP request smuggling attacks.
How do I fix CVE-2026-23941?
To mitigate CVE-2026-23941, upgrade your Erlang OTP and inets versions to the latest patched releases.
What types of software are affected by CVE-2026-23941?
CVE-2026-23941 affects Erlang/OTP versions from 17.0 to 28.4.1 and inets versions from 5.10 to 9.6.1.
What is HTTP request smuggling in CVE-2026-23941?
HTTP request smuggling is a technique used by attackers to interfere with the processing of HTTP requests by exploiting inconsistencies in parsing.
Are there any workarounds for CVE-2026-23941?
Currently, it is recommended to implement server configuration reviews and strict validation of headers as a temporary workaround until the software is updated.