GHSA-MRW5-54XQ-R399
Vulnerability from github – Published: 2026-08-15 06:32 – Updated: 2026-08-15 06:32In 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.
{
"affected": [],
"aliases": [
"CVE-2026-72321"
],
"database_specific": {
"cwe_ids": [],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2026-08-15T06:22:05Z",
"severity": null
},
"details": "In the Linux kernel, the following vulnerability has been resolved:\n\nipv4: igmp: Fix potential memory leaks in igmp_mod_timer() and igmp_stop_timer()\n\nWhen a timer is deleted and not re-armed in igmp_mod_timer(), or stopped\nin igmp_stop_timer(), the code currently decrements the reference counter\nof the multicast list entry @im using refcount_dec(\u0026im-\u003erefcnt).\n\nHowever, both functions can be called from the RCU reader path:\n- igmp_mod_timer() via igmp_heard_query() -\u003e for_each_pmc_rcu()\n- igmp_stop_timer() via igmp_rcv() -\u003e igmp_heard_report()\n\nIf the group im was concurrently removed from the list by ip_mc_dec_group(),\nits reference count might have already been decremented to 1.\n\nIn this case, timer_delete() succeeds, and refcount_dec() decrements\nthe refcount from 1 to 0. Since refcount_dec() does not free the object\nwhen it hits 0 (unlike ip_ma_put()), the im structure is leaked.\n\nFix this by using ip_ma_put(im) instead of refcount_dec(\u0026im-\u003erefcnt),\nand deferring the put until after the spinlock is released.",
"id": "GHSA-mrw5-54xq-r399",
"modified": "2026-08-15T06:32:20Z",
"published": "2026-08-15T06:32:20Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2026-72321"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/3546deaa0c30a14c7cdb5dc8f2432cb428f0cd36"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/95128dc74425ec19ed4f2077ccc651e791ff4b75"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/f60ec3058a85447008b88b762c859d336163acb3"
}
],
"schema_version": "1.4.0",
"severity": []
}
Sightings
| Author | Source | Type | Date | Other |
|---|
Nomenclature
- Seen: The vulnerability was mentioned, discussed, or observed by the user.
- Confirmed: The vulnerability has been validated from an analyst's perspective.
- Published Proof of Concept: A public proof of concept is available for this vulnerability.
- Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
- Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
- Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
- Not confirmed: The user expressed doubt about the validity of the vulnerability.
- Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.