CVE-2026-66357 inets,httpd:HTTP Request Smuggling via obs-fold Header Continuation
Attackers can perform HTTP request smuggling against Erlang OTP inets httpd due to missing obs-fold header continuation support, bypassing security controls.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-66357?
CVE-2026-66357 is a high-severity vulnerability in Erlang OTP, published on 1 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
httpd has never implemented obs-fold (RFC 2616 §2.2 / RFC 7230 §3.2.4 header continuation lines). Every CRLF followed by a non-CRLF octet unconditionally starts a new header. This missing feature became a security concern as the understanding of HTTP request smuggling attacks evolved.
This issue affects OTP from OTP 17.0 before OTP 27.3.4.17, from OTP 28.0 before OTP 28.5.0.6, and from OTP 29.0 before OTP 29.0.6, corresponding to inets from 5.10 before 9.3.2.7, from 9.4 before 9.6.2.3, and from 9.7 before 9.7.2. Whether OTP before OTP 17.0, corresponding to inets before 5.10, is affected is unknown.
Weakness: CWE-444
Which versions are affected by CVE-2026-66357?
How do I fix CVE-2026-66357?
Upgrade to a fixed version.
Is CVE-2026-66357 being exploited?
There is no known exploitation of CVE-2026-66357 in the wild and no public exploit code.
Sources
Also known as AZL-98460, DEBIAN-CVE-2026-66357, EEF-CVE-2026-66357, GHSA-qh2f-33hj-37qf, UBUNTU-CVE-2026-66357.