OpenSIPS prior 3.6.6/4.0.0-rc1 TCP Message Framing Layer integer overflow

Summaryinfo

A vulnerability labeled as very critical has been found in OpenSIPS. Affected by this vulnerability is an unknown functionality of the component TCP Message Framing Layer. Executing a manipulation can lead to integer overflow. This vulnerability is registered as CVE-2026-45103. It is possible to launch the attack remotely. No exploit is available.

Detailsinfo

A vulnerability was found in OpenSIPS. It has been declared as very critical. This vulnerability affects an unknown part of the component TCP Message Framing Layer. The manipulation with an unknown input leads to a integer overflow vulnerability. The CWE definition for the vulnerability is CWE-190. The product performs a calculation that can produce an integer overflow or wraparound, when the logic assumes that the resulting value will always be larger than the original value. This can introduce other weaknesses when the calculation is used for resource management or execution control. As an impact it is known to affect confidentiality, integrity, and availability. CVE summarizes:

OpenSIPS is a Session Initiation Protocol (SIP) server implementation. In versions prior to 3.6.6 and 4.0.0-rc1, the TCP message framing layer parses the Content-Length header using unsigned int arithmetic with no overflow check. When an attacker sends a Content-Length value that overflows unsigned int (e.g., 4294967296), the framing layer computes a wrapped-around value (e.g., 0) and splits the TCP stream at the wrong boundary, causing the body of the first SIP message to be processed as a separate message and enabling SIP message smuggling. Because Content-Length is parsed in the transport layer before authentication, an unauthenticated, network-based attacker can smuggle arbitrary SIP messages over any TCP-based transport (proto_tcp, proto_tls, proto_ws, proto_wss) on any instance with TCP enabled, with no routing-script preconditions. This allows smuggled messages to bypass front-end SBC/proxy security policies, inherit the connection's authentication context, and evade rate limiting. This issue has been fixed in versions 3.6.6 and 4.0.0-rc1.

The advisory is available at github.com. This vulnerability was named CVE-2026-45103 since 05/08/2026. The exploitation appears to be easy. The attack can be initiated remotely. No form of authentication is required for a successful exploitation. The technical details are unknown and an exploit is not available. The structure of the vulnerability defines a possible price range of USD $0-$5k at the moment (estimation calculated on 08/05/2026).

Upgrading to version 3.6.6 or 4.0.0-rc1 eliminates this vulnerability.

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Productinfo

Name

• OpenSIPS

Website

• Product: https://github.com/OpenSIPS/opensips/

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