External risk intelligence

Linux Kernel SCTP Use-After-Free Vulnerability

CVE advisorySeverity: CRITICAL (CVSS 9.8)

CVE-2026-74688

This vulnerability exists within the Linux kernel's SCTP implementation. While SCTP is a network protocol that can be exposed to the internet, it is typically used for specific transport requirements rather than as a general-purpose public-facing web or application service. Exposure depends heavily on the specific deployment and network configuration of the host.

Use After Free

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

External exposure likelihood

Horizon Alert

Summary of the vulnerability and why it matters

A critical vulnerability has been identified in the Linux kernel's implementation of the Stream Control Transmission Protocol (SCTP). This issue could allow for unauthorized access and manipulation of data. The main concern at this time is confirming whether this specific technology is in use and, if so, to what extent.

Critical flaw in Linux kernel's data transport.
Affects how data is managed and protected.
Confirm relevance and exposure to understand impact.

Attack Path

How an attacker could exploit the issue

An attacker could exploit this vulnerability by sending specially crafted network packets to a Linux system running a vulnerable kernel. This would involve targeting the Stream Control Transmission Protocol (SCTP) component, which is used for reliable, ordered, and error-checked packet delivery. If successful, the attacker could trigger a use-after-free condition, potentially leading to a system crash or allowing for arbitrary code execution.

Entry condition: Network exposure of SCTP.
Trigger point: Sending specific network packets.
Resulting risk: System instability or code execution.

Live Threat

Current exploitation, exposure, and threat context

In the Linux kernel, a vulnerability in the SCTP (Stream Control Transmission Protocol) implementation could allow for a use-after-free error. This occurs when a control chunk is queued for transmission but its associated transport is removed, leaving a dangling pointer. When the chunk is eventually sent, the system attempts to dereference this stale pointer, potentially leading to instability or other undefined behavior.

System stability could be affected.
A queued chunk might trigger a crash.
Denial of service is a potential outcome.

Operational Fix

Recommended remediation, mitigation, and detection steps

This vulnerability in the Linux kernel's SCTP implementation requires immediate attention from infrastructure and platform teams. The first practical step is to identify all Linux systems utilizing SCTP, determine their network exposure and business criticality, and then locate the system owner to plan remediation.

Identify SCTP systems and exposure.
Confirm system ownership and criticality.
Plan and execute remediation.

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 component?

SCTP, or Stream Control Transmission Protocol, is a transport-layer protocol in the Linux kernel that provides reliable, message-oriented communication. Unlike TCP, it supports multi-streaming and multi-homing, making it useful for specialized applications like telecommunications signaling (SS7/Diameter) and some high-availability database connections that require precise control over packet delivery and session management.

What does use-after-free mean for CVE-2026-74688?

This is a memory corruption flaw. It happens when the system tries to use a piece of memory after it has already been freed or cleared. In this CVE, the kernel keeps a reference to a transport path for a queued control message. If that path is deleted, the reference becomes 'dangling.' If the system later attempts to send that message, it accesses that invalid memory, which can cause the kernel to crash or potentially allow unintended memory manipulation.

How is this vulnerability triggered?

The condition requires a specific sequence involving SCTP HEARTBEAT ACK messages. It occurs when a control chunk is queued but the associated network path is removed before the chunk is sent. Normal SCTP traffic that does not encounter this specific race condition regarding queued control chunks and transport removal will not trigger the bug. It is a highly specific internal state error rather than a common interaction.

Do I need to worry if my system is internal?

According to Halo Surface Signal, this vulnerability is classified as external because the attack vector is network-based, but actual risk depends on your specific environment. If your systems are not exposed to the internet and are strictly managed within an internal network, the likelihood of an attacker reaching the SCTP stack is significantly lower. Evaluate whether your services running SCTP are reachable by untrusted parties.

When should I take action for this CVE?

You should prioritize this if your infrastructure relies on SCTP for network services. Your first step is to perform an inventory of Linux assets to find where SCTP is active. Once identified, evaluate the network exposure of those specific hosts. Coordinate with system owners to determine the criticality of these services and prepare to apply kernel updates provided by your distribution vendor as they become available.

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.