CVE-2026-66357: inets,httpd:HTTP Request Smuggling via obs-fold Header Continuation

High severity · published Sep 1, 2026

CVE-2026-66357

inets,httpd:HTTP Request Smuggling via obs-fold Header Continuation

8.3

CVSS

0.6%

EPSS

On KEV

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.

Exploitation

Is it being used?

Exploit prediction (EPSS)0.6% · higher than 47% of CVEs

Exploited in the wildNo evidence yet

CISA KEVNot listed

Ransomware campaign useNot known

Affected products

Which versions

OTP · Erlang

17.0 before 27.3.4.17; 28.0 before 28.5.0.6; 29.0 before 29.0.6; 5.10 before 9.3.2.7; 9.4 before 9.6.2.3; 9.7 before 9.7.2; +1 more · source: vendor

Affected product

OTP