CVE-2026-66357
HighCVSS 8.3Summary
The inets HTTP server in Erlang/OTP does not implement obs-fold (header continuation lines), which may lead to HTTP request smuggling vulnerabilities. Every CRLF followed by a non-CRLF starts a new header, which can be exploited by an attacker.
Risk Assessment
An attacker can exploit this to smuggle requests, potentially leading to session integrity issues, attacks on other systems, or privilege escalation.
Recommendation
Update Erlang/OTP to a patched version (OTP 27.3.4.17, 28.5.0.6, or 29.0.6) or apply additional protections such as proxy-level filters.
Other vulnerabilities in Erlang/OTP inets
See all- CVE-2026-74994Medium
The mod_auth module in OTP's inets httpd server, when configured with dets or mnesia authentication backends and multiple directory configuration blocks, collapses all directory blocks into a single shared user/group namespace. A user added to one protected directory is accepted as valid for all other protected directories on the same server instance.
- CVE-2026-73270High
A vulnerability in the inets HTTP server in Erlang/OTP allows a remote unauthenticated attacker to read files in a mod_auth protected directory by requesting them with different casing, on case-insensitive filesystems. The path check does not use the caseless option, allowing authentication bypass.
- CVE-2026-71562Medium
The httpc module in Erlang/OTP inets has an improper validation of specified quantity vulnerability. A malicious or compromised HTTP server can degrade availability by returning a numeric header with a very long run of digits, causing expensive integer conversion.
- CVE-2026-71380High
A vulnerability in the inets HTTP server in Erlang/OTP allows a remote unauthenticated attacker to cause denial of service by sending valid headers with a large Content-Length and then stalling. The server cancels the request timeout after header parsing and does not re-arm it, leaving workers waiting indefinitely.
- CVE-2026-70399High
A vulnerability in the inets HTTP server in Erlang/OTP allows a remote unauthenticated attacker to cause denial of service by opening and holding many connections. The max_clients option is not set by default, allowing unlimited simultaneous connections, leading to resource exhaustion.
- CVE-2026-66835High
A vulnerability in the inets HTTP server in Erlang/OTP allows a remote unauthenticated attacker to read files in a mod_auth protected directory by prefixing the request path with an extra slash. URI normalization does not collapse double slashes, causing the path check to miss the protected directory.
Original NVD description (English source)
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.