CVE-2026-72321

Technical 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 afte

Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

References