Erlang OTP httpd request smuggling

Summaryinfo

A vulnerability was found in Erlang OTP. It has been rated as problematic. This affects an unknown function of the component httpd. The manipulation leads to request smuggling. This vulnerability is documented as CVE-2026-66357. The attack can be initiated remotely. There is not any exploit available.

Detailsinfo

A vulnerability was found in Erlang OTP (version unknown). It has been rated as problematic. This issue affects an unknown function of the component httpd. The manipulation with an unknown input leads to a request smuggling vulnerability. Using CWE to declare the problem leads to CWE-444. The product acts as an intermediary HTTP agent (such as a proxy or firewall) in the data flow between two entities such as a client and server, but it does not interpret malformed HTTP requests or responses in ways that are consistent with how the messages will be processed by those entities that are at the ultimate destination. Impacted is integrity. The summary by CVE is:

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.

It is possible to read the advisory at github.com. The identification of this vulnerability is CVE-2026-66357 since 08/17/2026. The exploitation is known to be easy. The attack may be initiated remotely. No form of authentication is needed for a successful exploitation. The technical details are unknown and an exploit is not publicly available. The pricing for an exploit might be around USD $0-$5k at the moment (estimation calculated on 09/01/2026).

There is no information about possible countermeasures known. It may be suggested to replace the affected object with an alternative product.

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Productinfo

Vendor

• Erlang

Name

• OTP

Website

• Product: https://github.com/erlang/otp/

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