CVE-2026-23941: Erlang Erlang/inets

Critical severity, CVSS 9.4. EPSS: 0.5% chance of exploitation in the next 30 days.

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 before OTP 28.4.1, OTP 27.3.4.9 and OTP 26.2.5.18, corresponding to inets from 5.10 before 9.6.1, 9.3.2.3 and 9.1.0.5.

Affected products

• Erlang Erlang/inets: from 5.10, before 9.1.0.5 (fixed in 9.1.0.5); from 9.3, before 9.3.2.3 (fixed in 9.3.2.3); from 9.6, before 9.6.1 (fixed in 9.6.1)
• Erlang Erlang/otp: from 17.0, before 26.2.5.18 (fixed in 26.2.5.18); from 27.0, before 27.3.4.9 (fixed in 27.3.4.9); from 28.0, before 28.4.1 (fixed in 28.4.1)

Published 2026-03-13. Last modified 2026-07-24.