CVE-2026-72321

Received Received - Intake

Memory Leak in Linux Kernel IPv4 IGMP Timer Handling

Publication date: 2026-08-15

Last updated on: 2026-08-17

Assigner: kernel.org

Description

In the Linux kernel, the following vulnerability has been resolved: ipv4: igmp: Fix potential memory leaks in igmp_mod_timer() and igmp_stop_timer() When a timer is deleted and not re-armed in igmp_mod_timer(), or stopped in igmp_stop_timer(), the code currently decrements the reference counter of the multicast list entry @im using refcount_dec(&im->refcnt). However, both functions can be called from the RCU reader path: - igmp_mod_timer() via igmp_heard_query() -> for_each_pmc_rcu() - igmp_stop_timer() via igmp_rcv() -> igmp_heard_report() If the group im was concurrently removed from the list by ip_mc_dec_group(), its reference count might have already been decremented to 1. In this case, timer_delete() succeeds, and refcount_dec() decrements the refcount from 1 to 0. Since refcount_dec() does not free the object when it hits 0 (unlike ip_ma_put()), the im structure is leaked. Fix this by using ip_ma_put(im) instead of refcount_dec(&im->refcnt), and deferring the put until after the spinlock is released.

CVSS Scores

EPSS Scores

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Meta Information

Published

2026-08-15

Last Modified

2026-08-17

Generated

2026-09-04

AI Q&A

2026-08-15

EPSS Evaluated

2026-09-03

NVD

CVE-2026-72321

EUVD

EUVD-2026-59220

Affected Vendors & Products

Vendor	Product	Version / Range
linux	linux_kernel	*

Helpful Resources

Exploitability

CWE

KEV

CWE ID	Description
CWE-UNKNOWN

Attack-Flow Graph

Executive Summary

This vulnerability in the Linux kernel involves memory leaks in the IGMP (Internet Group Management Protocol) timer functions. When a timer is deleted or stopped without being re-armed, the code incorrectly decrements the reference counter of a multicast list entry. If the entry was concurrently removed, this can lead to the reference count reaching zero without freeing the memory, causing a memory leak.

Detection Guidance

This vulnerability is specific to the Linux kernel's IPv4 IGMP implementation and may not have direct detection commands. Monitor kernel logs for memory leaks or crashes related to multicast group handling. Check for unusual network traffic patterns involving IGMP queries or reports.

Impact Analysis

This vulnerability can lead to memory leaks in the Linux kernel, which may cause system instability, performance degradation, or crashes over time due to excessive memory consumption. Systems relying on multicast networking, such as those using IGMP for group management, are particularly affected.

Compliance Impact

This vulnerability is a memory leak in the Linux kernel's IPv4 IGMP timer handling, which does not directly impact compliance with standards like GDPR or HIPAA. Memory leaks may lead to resource exhaustion but do not typically violate data protection or privacy requirements unless they cause system instability affecting data processing.

Mitigation Strategies

Apply the latest Linux kernel security patches that include the fix for this issue. If immediate patching is not possible, consider disabling IPv4 multicast or restricting multicast traffic until the patch is applied.

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