CVE-2026-23941 Request smuggling via first-wins Content-Length parsing in inets httpd
Attackers can exploit HTTP request smuggling in Erlang OTP inets httpd by sending duplicate Content-Length headers, causing desynchronization with reverse proxies.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-23941?
CVE-2026-23941 is a high-severity vulnerability in Erlang OTP, published on 13 Mar 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
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.
Weakness: CWE-444
Which versions are affected by CVE-2026-23941?
It affects 2 products.
Products include Erlang Erlang\/Inets, Erlang Erlang\/Otp.
How do I fix CVE-2026-23941?
Upgrade to a fixed version.
Is CVE-2026-23941 being exploited?
There is no known exploitation of CVE-2026-23941 in the wild and no public exploit code.
Other vulnerabilities in Erlang OTP
- CVE-2026-28808 ScriptAlias CGI targets bypass directory auth in inets httpd (mod_auth vs mod_cgi path mismatch)
- CVE-2026-48856 httpc leaks Authorization header to cross-origin redirect targets
- CVE-2026-48858 ftp client PASV response IP not validated against control peer, enabling SSRF and FTP bounce attacks
Sources
Also known as AZL-79880, DEBIAN-CVE-2026-23941, EEF-CVE-2026-23941, GHSA-w4jc-9wpv-pqh7, UBUNTU-CVE-2026-23941.