In the Linux kernel, a vulnerability identified as CVE-2025-21648 has been discovered, which impacts the conntrack hashtable resizing process. This vulnerability is classified as medium severity with a CVSS score of 5.5. If left unaddressed, it can lead to significant availability issues within systems utilizing the Linux kernel.
The vulnerability allows for a condition where the maximum size of the conntrack hashtable is not correctly constrained, potentially leading to a WARN_ON_ONCE trigger in the memory allocation function __kvmalloc_node_noprof(). This issue arises because the flag __GFP_NOWARN is unset during resizing operations. Organizations utilizing vulnerable versions of the Linux kernel should be aware of the risk this poses.
Given the nature of this vulnerability and its exploitation potential, organizations should prioritize patching immediately. Multiple versions of the Linux kernel are affected by this vulnerability, and it is crucial to apply the necessary updates to mitigate any risk.
The vulnerability was published on January 19, 2025, and has since been modified. Organizations must ensure that they are running the latest kernel versions to avoid this vulnerability.
Vulnerability Details
The official description highlights that this vulnerability allows the conntrack hashtable size to exceed the maximum limit defined as INT_MAX. This can result in the kernel triggering an error during memory allocation as it attempts to resize the hashtable. The kernel version must be updated to address this issue effectively.
The CVSS score for this vulnerability is 5.5, categorizing it as medium severity. The attack vector is local, meaning an attacker must have local access to exploit this vulnerability. The attack complexity is low, requiring only low privileges and no user interaction.
This vulnerability affects various versions of the Linux kernel, particularly those between 4.7.1 and 5.10.234, as well as 5.11 through 5.15.177, and others up to the 6.x series. The publication date for this vulnerability is January 19, 2025.
Technical Analysis
The root cause of this vulnerability lies in the incorrect handling of the maximum size for the conntrack hashtable. When the hashtable is resized, it can exceed the limits, leading to potential memory allocation errors. The resizing operation is only possible during the initialization phase of the network namespace.
The attack vector for this vulnerability is local, requiring an attacker to have local access to the system. The attack complexity is low, meaning that even users with low privileges can potentially exploit this vulnerability without requiring user interaction. The impacts on confidentiality and integrity are none, but the availability impact is high, which is critical for system operation.
Risk & Impact Analysis
Risk to organizations includes potential service disruptions due to the availability impact of this vulnerability. Should the conntrack hashtable fail to resize correctly, it could lead to a system crash or instability, affecting all applications relying on the Linux kernel.
The blast radius for this vulnerability can be significant, particularly in environments where the Linux kernel is widely deployed across production systems. Organizations should assess their exposure to this risk and take immediate action to remediate the vulnerability.
With a CVSS score of 5.5 and the absence from the Known Exploited Vulnerabilities (KEV) catalog, organizations should address this vulnerability in their priority patch cycle. The lack of public exploitation information does not mitigate the risk associated with this medium-severity vulnerability.
Exploitation Status
Signal | Status |
|---|---|
Known Exploit | No |
Public PoC | No |
Actively Exploited | No |
Ransomware Use | No |
Affected Versions
The following versions of the Linux kernel are affected by this vulnerability: - All versions from 4.7.1 up to, but not including, 5.10.234 - All versions from 5.11 up to, but not including, 5.15.177 - All versions from 5.16 up to, but not including, 6.1.125 - All versions from 6.2 up to, but not including, 6.6.72 - All versions from 6.7 up to, but not including, 6.12.10 - Specific release candidates of version 6.13
Mitigation & Remediation
Organizations should prioritize applying the latest patches to the Linux kernel to address this vulnerability. It is crucial to upgrade to versions that are not affected, specifically those released after the identified vulnerable ranges.
If patching is not immediately feasible, organizations may consider implementing configuration hardening practices to mitigate the risk while preparing to update the kernel. Additional network controls may also be necessary to limit exposure.
For further information on effective security testing and vulnerability management, organizations should consider engaging in penetration testing to validate their security posture.
Detection Guidance
Organizations should monitor logs for any anomalies related to conntrack operations. Key indicators include errors or warnings during hashtable resizing operations that could suggest attempts to exploit this vulnerability.
Behavioral anomalies in the network stack should also be assessed to identify potential abuse of the conntrack functionality. Any unexpected system behavior following kernel operations may warrant further investigation.
AppSecure Threat Intelligence Insight
The long-term significance of CVE-2025-21648 lies in its illustration of how local vulnerabilities can lead to serious availability issues, even without a direct impact on confidentiality or integrity. This necessitates robust vulnerability management practices.
Security teams should take note of the trends in kernel vulnerabilities, as they highlight the critical nature of maintaining up-to-date systems. Regular updates and monitoring for patches are essential components of a proactive security strategy.
Organizations can benefit from reviewing their security processes against best practices outlined in the penetration testing methodology to ensure comprehensive coverage against such vulnerabilities.
Furthermore, the evolving landscape of vulnerabilities, including those affecting the Linux kernel, underscores the need for organizations to engage in continuous security assessments, such as vulnerability management programs, to adapt to emerging threats.
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
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