CVE-2026-66357: inets,httpd:HTTP Request Smuggling via obs-fold Header Continuation
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.
Other sources
inets,httpd:HTTP Request Smuggling via obs-fold Header Continuation
— Microsoft
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Upgrade
Upgrade to a fixed release to a version that resolves this vulnerability.
Fixed in 26.2.5.21-6 - Upgrade
Upgrade
debian/erlangto a version that resolves this vulnerability.Fixed in 1:29.0.6+dfsg-1Fixed in 1:29.1.1+dfsg-1 - Upgrade
Upgrade
OTPto a version that resolves this vulnerability.Fixed in 27.3.4.17 - Upgrade
Upgrade
OTPto a version that resolves this vulnerability.Fixed in 28.5.0.6 - Upgrade
Upgrade
OTPto a version that resolves this vulnerability.Fixed in 29.0.6 - Upgrade
Upgrade
inetsto a version that resolves this vulnerability.Fixed in 9.3.2.7 - Upgrade
Upgrade
inetsto a version that resolves this vulnerability.Fixed in 9.6.2.3 - Upgrade
Upgrade
inetsto a version that resolves this vulnerability.Fixed in 9.7.2
Event History
Frequently Asked Questions
Which deployments are known to be affected?
Known affected releases are OTP 17.0 through before 27.3.4.17, OTP 28.0 through before 28.5.0.6, and OTP 29.0 through before 29.0.6. The corresponding affected inets ranges are 5.10 through before 9.3.2.7, 9.4 through before 9.6.2.3, and 9.7 through before 9.7.2.2.
Are releases older than OTP 17.0 affected?
It is unknown whether OTP releases before 17.0, corresponding to inets releases before 5.10, are affected.
What fixed versions are available?
Upgrade to OTP 27.3.4.17, 28.5.0.6, or 29.0.6, as applicable. The corresponding fixed inets versions are 9.3.2.7, 9.6.2.3, and 9.7.2.2.