CVE-2026-89476

A flaw was found in the Linux kernel's Stream Control Transmission Protocol (SCTP) implementation. A remote attacker could exploit this by sending specially crafted duplicate RECONF responses. This action can cause an underflow in the stream->outcnt counter, potentially leading to unexpected system behavior or a denial of service (DoS) condition.

An integer underflow in the SCTP stream reconfiguration handling can occur because strreset_outstanding was tracked as a counter instead of per request type state. A cached RECONF chunk may contain multiple request parameters, and a duplicate response can process the same ADD_OUT request again while another request is still outstanding, causing stream outcnt rollback to be applied twice. This can corrupt SCTP association stream accounting and may lead to denial of service, with a plausible worst case of limited confidentiality or integrity impact if the underflow drives later out of bounds stream handling. For the CVSS the PR:N value is used because a remote SCTP peer can trigger the protocol state after reaching an SCTP endpoint and establishing an association. The issue is network reachable for systems that expose SCTP services using stream reconfiguration, but practical exposure is limited to deployments where SCTP is enabled and reachable from untrusted peers.

The CVSS score(s) listed for this vulnerability do not reflect the associated product's status, and are included for informational purposes to better understand the severity of this vulnerability.

Mitigation for this issue is either not available or the currently available options don't meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base or stability.