CVE-2026-74670
Received Received - Intake

IPVS Estimator Use-After-Free in Linux Kernel

Publication date: 2026-08-22

Last updated on: 2026-08-22

Assigner: kernel.org

Description
In the Linux kernel, the following vulnerability has been resolved: ipvs: stop estimator after disabled calc phase IPVS estimator kthread 0 starts with zeroed chain and tick limits until its initial calculation phase completes. If network namespace teardown clears ipvs->enable during that phase, ip_vs_est_calc_phase() can return without installing positive limits. The kthread can then continue into its main loop and drain est_temp_list with zero chain_max, tick_max and est_max_count values. Each enqueue consumes one available tick row, but est_count never reaches the zero est_max_count value. After all rows are consumed, the row lookup returns IPVS_EST_NTICKS and ip_vs_enqueue_estimator() writes past the ticks and tick_len arrays. Exit kthread 0 after the calculation phase if the kthread is stopping or IPVS has been disabled. That keeps temporary estimators from being drained after the limits failed to initialize. Estimator kthreads can now self-exit before teardown or reload stops kd->task. Keep an extra task reference after creation and release it with kthread_stop_put(), so kd->task remains valid until the stop paths consume that reference.

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Meta Information

Published
2026-08-22
Last Modified
2026-08-22
Generated
2026-08-22
AI Q&A
2026-08-22
EPSS Evaluated
N/A
NVD
CVE-2026-74670
EUVD
EUVD-2026-64357

Affected Vendors & Products

Showing 1 associated CPE
Vendor Product Version / Range
linux linux_kernel *

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Exploitability

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CWE ID Description
CWE-UNKNOWN

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Executive Summary

This vulnerability in the Linux kernel involves the IPVS estimator kthread which may continue running even after IPVS is disabled during its initial calculation phase. This can lead to memory corruption as the kthread attempts to write past array bounds when processing temporary estimators with zeroed limits.

Detection Guidance

This vulnerability is specific to the Linux kernel's IPVS (IP Virtual Server) estimator functionality. Detection requires checking kernel logs for IPVS-related errors or crashes, particularly during network namespace teardown or IPVS module reload. Monitor for kernel oops messages or warnings about estimator kthreads. Commands like dmesg | grep -i ipvs or journalctl -k | grep -i ipvs may help identify issues. Ensure your kernel version is updated to the patched version.

Impact Analysis

If exploited, this flaw could cause system instability or crashes due to memory corruption. It may also lead to denial-of-service conditions if the affected kthread consumes excessive resources or corrupts critical kernel data structures.

Mitigation Strategies

Apply the latest kernel update that includes the fix for this vulnerability. If immediate patching is not possible, disable IPVS estimator functionality temporarily by unloading the ip_vs module or disabling IPVS in your configuration. Monitor kernel logs for any signs of exploitation or instability. Restrict access to network namespaces where IPVS is used to reduce attack surface.

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