In the Linux kernel, a high-severity vulnerability has been reported in the mptcp protocol. This vulnerability allows soft lockups when receiving data with MSG_PEEK and MSG_WAITALL flags. The issue arises because the skb is not removed from the sk_receive_queue, causing sk_wait_data() to continuously find available data, hence leading to a soft lockup. Organizations should prioritize patching immediately to address this critical issue.
The CVSS score for this vulnerability is 7.5, indicating a high severity level. The vulnerability can be exploited over the network with low complexity and does not require user interaction or privileges, making it particularly concerning for organizations relying on the affected kernel version.
Risk to organizations includes potential service disruptions due to the soft lockup issue, which could lead to unresponsive systems. Given that the vulnerability is not currently included in the Known Exploited Vulnerabilities (KEV) list, there may not be widespread exploitation reported at this time. However, proactive remediation is essential.
Organizations should address this vulnerability as part of their immediate patch management cycle to mitigate risks associated with availability impacts. Monitoring for any signs of exploitation is also advisable, considering the potential for future attacks leveraging this vulnerability.
Vulnerability Details
The vulnerability, identified as CVE-2026-43029, has been classified as a high-severity issue with a CVSS score of 7.5. It was published on May 1, 2026. The official description indicates that it has been resolved in the Linux kernel, specifically addressing a soft lockup in the mptcp_recvmsg() function.
The issue is rooted in the handling of message flags MSG_PEEK and MSG_WAITALL, where the skb is not removed from the sk_receive_queue. This error leads to sk_wait_data() never performing actual waiting, culminating in a soft lockup.
The fix involves adding a 'last' parameter to track the last peeked skb, enabling sk_wait_data() to make informed decisions and prevent infinite loops during MSG_PEEK usage.
Technical Analysis
The root cause of this vulnerability is the mishandling of socket buffer management within the Linux kernel's implementation of the mptcp protocol. Specifically, when data is received with the MSG_PEEK and MSG_WAITALL flags, the socket buffer (skb) is not removed, leading to continuous availability detection without actual data processing.
The attack vector is network-based, and the attack complexity is low, as no special privileges or user interaction is required to trigger the vulnerability.
The impact on availability is significant, as systems may become unresponsive due to the soft lockup. There are no confidentiality or integrity impacts associated with this vulnerability.
Risk & Impact Analysis
Organizations utilizing the Linux kernel with the mptcp protocol are at risk of service disruptions caused by this vulnerability. The potential for a soft lockup can lead to significant downtime, impacting business operations and service delivery.
With a CVSS score of 7.5, the urgency for patching is high. Organizations must prioritize this vulnerability in their patch management cycle, especially those operating critical systems that rely on the mptcp protocol.
The blast radius could extend to any services relying on the Linux kernel's network stack, making it crucial for security teams to assess their exposure and implement necessary patches promptly.
Exploitation Status
Signal | Status |
|---|---|
Known Exploit | No |
Public PoC | No |
Actively Exploited | No |
Ransomware Use | No |
Affected Versions
All versions of the Linux kernel prior to the fix are affected. Organizations should ensure they are running the latest patched version to mitigate the risks associated with this vulnerability.
Mitigation & Remediation
To remediate this vulnerability, organizations should apply the latest patches provided by the Linux kernel maintainers. If patches are not immediately available, consider implementing workarounds such as avoiding the use of MSG_PEEK and MSG_WAITALL flags in critical applications.
Configuration hardening should also be considered, including minimizing access to the affected services and implementing network segmentation to limit exposure.
Organizations can enhance their security posture by adopting a proactive approach through regular security assessments and penetration testing. Engaging in penetration testing can help identify similar weaknesses before they are exploited.
Detection Guidance
Organizations should monitor logs for indicators of unusual behavior associated with the mptcp protocol. This includes analyzing socket buffer management and monitoring for soft lockup messages in kernel logs.
Behavioral anomalies related to network performance should be scrutinized, and alerts should be configured to notify security teams of potential issues.
AppSecure Threat Intelligence Insight
The long-term significance of CVE-2026-43029 lies in its demonstration of the complexities involved in kernel-level networking implementations. As organizations increasingly depend on kernel capabilities, vulnerabilities like this highlight the need for robust testing and validation mechanisms.
Security teams should take this opportunity to refine their vulnerability management processes and consider adopting a vulnerability management program that prioritizes thorough testing of critical infrastructure.
Additionally, understanding similar vulnerabilities can help organizations prepare for future risks. The adoption of regular security assessments, such as penetration testing methodology, can aid in identifying and mitigating such weaknesses proactively.
In conclusion, CVE-2026-43029 serves as a reminder of the critical importance of maintaining updated systems and the need for ongoing vigilance against potential vulnerabilities within the Linux kernel and its associated protocols.
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
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