CVE-2026-23457

In the Linux kernel, the following vulnerability has been resolved:

netfilter: nf_conntrack_sip: fix Content-Length u32 truncation in sip_help_tcp()

sip_help_tcp() parses the SIP Content-Length header with

simple_strtoul(), which returns unsigned long, but stores the result in

unsigned int clen. On 64-bit systems, values exceeding UINT_MAX are

silently truncated before computing the SIP message boundary.

For example, Content-Length 4294967328 (2^32 + 32) is truncated to 32,

causing the parser to miscalculate where the current message ends. The

loop then treats trailing data in the TCP segment as a second SIP

message and processes it through the SDP parser.

Fix this by changing clen to unsigned long to match the return type of

simple_strtoul(), and reject Content-Length values that exceed the

remaining TCP payload length.