External risk intelligence

Linux Kernel SCTP Vulnerability Leads to Information Disclosure and Denial of Service.

CVE advisorySeverity: CRITICAL (CVSS 9.8)

CVE-2026-89478

This vulnerability exists in the Linux kernel SCTP implementation. While SCTP is a network protocol, its use in common deployments varies widely; it is not consistently exposed as a public-facing service in the same manner as standard web or management interfaces, making internet reachability possible but not inherently typical or guaranteed across all deployments.

Halo Surface Signal: 3 out of 5 — possibly public-facing.

External exposure likelihood

Horizon Alert

Summary of the vulnerability and why it matters

This vulnerability affects the Linux kernel's handling of network communication protocols, specifically the Stream Control Transmission Protocol (SCTP). It could allow for a denial of service or more severe impacts if an attacker can exploit a timing issue during communication handling. The main concern is confirming if this specific protocol is in active use within your environment.

An error in network protocol handling.
Potentially serious impact on system stability.
Confirm if this network protocol is used.

Attack Path

How an attacker could exploit the issue

An attacker could exploit this vulnerability by sending a specially crafted ASCONF DEL-IP message to a system using the Linux kernel's SCTP implementation. This message could cause a critical race condition, leading to a use-after-free vulnerability when processing subsequent network packets. If successful, this could allow an attacker to crash the system or potentially execute arbitrary code.

Entry Condition: Authenticated user with ASCONF DEL-IP capability.
Trigger Point: Processing a DATA chunk after transport removal.
Resulting Risk: System crash or arbitrary code execution.

Live Threat

Current exploitation, exposure, and threat context

This vulnerability in the Linux kernel's SCTP implementation could allow a malicious actor to cause a denial of service or potentially impact system integrity. When a transport is removed, a race condition may allow a subsequent data chunk to use the removed transport, leading to the processing of freed memory. This could occur when an authenticated user sends an ASCONF DEL-IP message while SCTP packets are in transit or on the socket backlog.

Kernel memory could be corrupted.
Malicious packets could be sent.
System stability may be impacted.

Operational Fix

Recommended remediation, mitigation, and detection steps

In real-world scenarios, teams responsible for the Linux kernel, likely infrastructure or platform teams, must first identify where the affected SCTP functionality is deployed. Confirming its reachability and business criticality is essential to assign ownership and plan remediation effectively.

Infrastructure/Platform teams own the issue.
Verify SCTP usage and external exposure.
Plan remediation based on confirmed risk.

Supplementary metadata

CVSS vector

Validate whether this threat affects your internet-facing exposure.

Halo Threat Intelligence helps prioritize remediation with Halo Surface Signal and H/A/L/O context. Start exposure validation with a free external attack surface trial.

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Frequently asked questions

What is the Linux kernel SCTP implementation affected by CVE-2026-89478?

SCTP, or Stream Control Transmission Protocol, is a transport-layer protocol within the Linux kernel that facilitates reliable data delivery between networked systems. It is often used for specialized communication tasks that require features like multi-homing or multi-streaming, distinguishing it from more common protocols like TCP or UDP.

How does this Linux kernel vulnerability work?

This vulnerability is a use-after-free condition. It occurs when a network transport path is deleted while an SCTP packet is still being processed. Because the system may attempt to read information from that deleted path later, it accesses memory that has already been freed, which can cause system instability or allow for unauthorized code execution.

Do I need to be concerned about specific network actions triggering this bug?

Yes, exploitation relies on a specific sequence involving an ASCONF DEL-IP message. This command tells the system to remove an IP address from an existing SCTP association. The vulnerability is triggered during the race condition that occurs if data chunks are processed at the exact moment this removal happens; it does not trigger during standard, stable communication sessions where no transport removal is requested.

Is my system at risk according to Halo Surface Signal?

Halo Surface Signal notes that while this vulnerability affects the Linux kernel, SCTP is not always exposed as a public-facing service. The risk depends on whether your systems actively use SCTP and whether those specific services are reachable over the internet. You should verify if your infrastructure relies on SCTP, as it is not universally active in every deployment.

When should I prioritize fixing CVE-2026-89478?

First, consult your infrastructure or platform teams to identify which servers or applications in your environment utilize the SCTP protocol. Once you have mapped these assets and determined which ones are reachable over the network, prioritize patching systems where SCTP is a business-critical or externally exposed component to mitigate the risk of system crashes or memory corruption.

References

Written by Nicholas Merritt

Nicholas Merritt is VP of Security Solutions at Halo Security. With more than 25 years across application security, vulnerability prioritization, and offensive security, he helps teams translate threat data into practical exposure validation and remediation focus. He authors Halo Threat Intelligence CVE advisories using Halo Surface Signal and H/A/L/O context to prioritize internet-facing risk.