Double-Free — CraftedSignal Threat Feed

CVE-2026-31507 Double-Free Vulnerability in net/smc

hello@craftedsignal.io — Thu, 23 Apr 2026 07:27:47 +0000

On April 23, 2026, Microsoft published a security update guide addressing CVE-2026-31507, a double-free vulnerability residing in the net/smc (Sockets Multiplexing Controller) module of the Linux kernel. The vulnerability stems from a flaw in how the tee() function handles the duplication of splice pipe buffers. Specifically, when tee() duplicates a splice pipe buffer associated with the smc_spd_priv structure, it can lead to a double-free condition. This flaw could allow a local attacker to trigger memory corruption or a denial-of-service condition. While specific exploitation details are currently lacking, the nature of double-free vulnerabilities makes them a critical concern for system stability and security.

Attack Chain

A local attacker gains access to the system.
The attacker crafts a malicious program that interacts with the net/smc module.
The program triggers the tee() function to duplicate a splice pipe buffer related to smc_spd_priv.
Due to the vulnerability, the same memory region associated with smc_spd_priv is freed twice.
The double-free corrupts the heap metadata.
Subsequent memory allocations may lead to arbitrary code execution or denial-of-service.
The attacker could leverage the memory corruption to escalate privileges.
Successful exploitation results in system compromise.

Impact

Successful exploitation of CVE-2026-31507 can lead to memory corruption, potentially enabling arbitrary code execution and privilege escalation. A more likely outcome is a denial-of-service condition, where the system becomes unstable or crashes due to heap corruption. The vulnerability affects systems utilizing the affected net/smc module. While the number of potential victims is unknown, the wide deployment of the Linux kernel makes this a significant concern.

Recommendation

Apply the security patch provided by Microsoft that addresses CVE-2026-31507 to mitigate the double-free vulnerability.
Monitor systems for unusual tee() function calls within the net/smc module using a process creation rule with relevant command-line arguments and process ancestry.

CVE-2026-33824: Windows IKE Extension Double Free Vulnerability

hello@craftedsignal.io — Wed, 15 Apr 2026 12:00:00 +0000

CVE-2026-33824 is a critical vulnerability affecting the Windows Internet Key Exchange (IKE) Extension. This double-free vulnerability enables an unauthenticated attacker to execute arbitrary code on a vulnerable system remotely. The vulnerability stems from improper memory management within the IKE service. Successful exploitation could lead to complete system compromise, making it a high-priority concern for defenders. Microsoft has assigned a CVSS v3.1 score of 9.8 to this vulnerability. This issue was reported to Microsoft and assigned CVE-2026-33824. The affected systems are those running the Windows IKE Extension without the necessary security update.

Attack Chain

An unauthenticated attacker sends a specially crafted IKE packet to the target system.
The Windows IKE Extension processes the malicious IKE packet.
Due to a flaw in memory management, the IKE Extension attempts to free the same memory location twice (double-free).
The double-free condition corrupts the heap memory.
The attacker leverages the heap corruption to overwrite critical data structures.
The attacker gains control of program execution flow.
The attacker injects and executes arbitrary code within the context of the IKE service.
The attacker achieves remote code execution, potentially leading to complete system compromise.

Impact

Successful exploitation of CVE-2026-33824 allows a remote, unauthenticated attacker to execute arbitrary code on a vulnerable Windows system. Given the critical CVSS score of 9.8, the impact is severe. A compromised system could be used to steal sensitive data, establish a foothold for further network penetration, or cause a denial-of-service condition. Organizations that do not apply the patch released by Microsoft are at significant risk of compromise.

Recommendation

Apply the security update released by Microsoft to patch CVE-2026-33824 on all affected Windows systems immediately. Refer to the Microsoft advisory https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-33824.
Monitor network traffic for suspicious IKE packets targeting your Windows systems. Deploy the network connection rule below to identify potential exploitation attempts.
Enable Windows event logging for the IKE service and deploy the process creation rule below to detect unexpected processes spawned by the IKE service.

CVE-2026-26179 Windows Kernel Double Free Privilege Escalation

hello@craftedsignal.io — Wed, 15 Apr 2026 12:00:00 +0000

CVE-2026-26179 is a critical security vulnerability residing within the Windows Kernel. This double-free vulnerability allows an attacker with local access to elevate their privileges. Successful exploitation grants the attacker higher-level permissions on the compromised system. The vulnerability was reported to Microsoft and assigned a CVSS v3.1 score of 7.8, indicating a high severity. The vulnerability lies within the core operating system components, making it a significant threat to Windows-based environments. Exploitation of this vulnerability requires an attacker to have valid local credentials on the target system. The vulnerability was published on 2026-04-14.

Attack Chain

An attacker gains initial local access to a Windows system through legitimate credentials or by exploiting another vulnerability.
The attacker crafts a malicious program designed to trigger the double-free condition in the Windows Kernel.
The malicious program interacts with a vulnerable kernel function, likely through a specific system call (Nt*).
The vulnerable kernel function attempts to free the same memory region twice due to a logical error.
The double-free corrupts the kernel’s memory management structures, such as the heap metadata.
The memory corruption allows the attacker to overwrite critical kernel data structures, such as process tokens or privilege attributes.
The attacker modifies the process token of their own process, elevating their privileges to SYSTEM or another highly privileged account.
The attacker now executes privileged commands and gains full control over the system.

Impact

Successful exploitation of CVE-2026-26179 allows a local attacker to elevate privileges to SYSTEM, the highest level of privilege on a Windows system. This grants the attacker complete control over the compromised machine, allowing them to install software, modify data, create new accounts, and access sensitive information. A successful privilege escalation can lead to a complete compromise of the confidentiality, integrity, and availability of the system. This vulnerability affects all Windows systems where the patch has not been applied.

Recommendation

Apply the security update provided by Microsoft to patch CVE-2026-26179 as soon as possible.
Monitor systems for unusual process creation events originating from user accounts, as this could be an indicator of exploit activity. Deploy the provided Sigma rule Detect Suspicious Process Token Modifications to identify potential privilege escalation attempts.
Enable process auditing and monitor for unusual system calls using tools like Sysmon to catch the initial exploitation attempts.
Regularly review and enforce the principle of least privilege to limit the impact of successful local exploits.
Deploy the Sigma rule Detect Double Free Vulnerability Exploitation to identify exploitation of double free vulnerabilities by monitoring process creation and memory allocation patterns.

CVE-2026-31609 SMB Client Double-Free Vulnerability

hello@craftedsignal.io — Wed, 24 Jan 2024 12:00:00 +0000

CVE-2026-31609 is a double-free vulnerability affecting the SMB (Server Message Block) client. The vulnerability resides in the smbd_free_send_io() function, which is called after smbd_send_batch_flush(). A double-free vulnerability occurs when memory is freed twice, potentially leading to corruption of the heap and potentially allowing an attacker to execute arbitrary code. The specifics of exploitation are not detailed in the initial advisory but successful exploitation could lead to a complete compromise of the affected system. This vulnerability demands immediate attention from security teams due to the potential for remote code execution and the widespread use of the SMB protocol in networked environments.

Attack Chain

An attacker crafts a malicious SMB request designed to trigger the smbd_send_batch_flush() function within the SMB client.
The smbd_send_batch_flush() function executes, processing the crafted SMB request.
Due to a flaw in the logic, the same memory is passed twice to a free() call within smbd_free_send_io().
The first free() call deallocates the memory as intended.
The second free() call attempts to deallocate the already freed memory, causing a double-free condition.
This double-free corrupts the heap metadata, creating an opportunity for an attacker to manipulate memory allocation.
The attacker exploits the heap corruption to overwrite critical data structures within the SMB client process.
By overwriting function pointers or other sensitive data, the attacker gains control of the execution flow, leading to arbitrary code execution.

Impact

Successful exploitation of CVE-2026-31609 could allow an attacker to execute arbitrary code on the affected system with the privileges of the SMB client. Given the widespread use of SMB for file sharing and network communication, this vulnerability could be leveraged to gain unauthorized access to sensitive data, install malware, or disrupt critical services. The impact could range from data breaches and ransomware attacks to complete system compromise and lateral movement within a network.

Recommendation

Apply the security update provided by Microsoft to patch CVE-2026-31609 as soon as possible.
Enable SMB auditing to monitor for suspicious SMB traffic and potential exploitation attempts.
Deploy the following Sigma rule to detect potential exploitation attempts by monitoring for unusual SMB client process behavior.