CVE-2026-45103 OpenSIPS: SIP Message Smuggling via TCP Content-Length Integer Overflow
Unauthenticated attackers can smuggle SIP messages via TCP Content-Length integer overflow, bypassing security policies and rate limits.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- None listed
What is CVE-2026-45103?
CVE-2026-45103 is a high-severity vulnerability in opensips, published on 4 Aug 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
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.
Weakness: CWE-190
Which versions are affected by CVE-2026-45103?
How do I fix CVE-2026-45103?
No fix has been published for CVE-2026-45103 yet. Limit exposure of the affected software until one is available.
Is CVE-2026-45103 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-45103 exists.
Sources
Also known as GHSA-jv35-555v-54jh, UBUNTU-CVE-2026-45103.