CVE-2026-89476: sctp: fix stream->outcnt underflow on duplicate RECONF responses
In the Linux kernel, the following vulnerability has been resolved:
sctp: fix stream->outcnt underflow on duplicate RECONF responses
A cached RECONF chunk may contain more than one request parameter. A duplicate response can therefore find and process the same ADDOUT request again while another parameter is still outstanding, rolling back outcnt twice and possibly underflowing it.
Track outstanding request types as bits and clear each bit after its first response. Later responses for the same request are then ignored.
Affected Software
Event History
Frequently Asked Questions
Which deployments should be assessed for exposure?
Systems running the Linux kernel with SCTP in use should be assessed, particularly where SCTP reconfiguration requests can be processed.
What protocol condition is required for the issue to occur?
A cached RECONF chunk must contain multiple request parameters, including an ADD_OUT request, and a duplicate response must be processed while another parameter remains outstanding. This can cause the same ADD_OUT request to be processed twice and decrement outcnt twice.