CVE-2026-66357: Erlang OTP

High severity, CVSS 8.3. EPSS: 0.6% chance of exploitation in the next 30 days.

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.

Affected products

• Erlang OTP: from 17.0, before 27.3.4.17 (fixed in 27.3.4.17); from 28.0, before 28.5.0.6 (fixed in 28.5.0.6); from 29.0, before 29.0.6 (fixed in 29.0.6); from 5.10, before 9.3.2.7 (fixed in 9.3.2.7); from 9.4, before 9.6.2.3 (fixed in 9.6.2.3); from 9.7, before 9.7.2 (fixed in 9.7.2)

Published 2026-09-01. Last modified 2026-09-08.