CVE-2026-98414

Received Received - Intake

Memory Leak in Linux Kernel Memory Controller

Publication date: 2026-10-14

Last updated on: 2026-10-19

Assigner: kernel.org

Description

In the Linux kernel, the following vulnerability has been resolved: memcg: avoid charging the root memcg from obj_cgroup_charge_pages() obj_cgroup_charge_pages() resolves the objcg to its memcg and calls try_charge_memcg(), which does not short circuit the root memcg. That memcg can be the root memcg: obj_cgroup_is_root() reflects the memcg the objcg was created for and is never updated, while memcg_reparent_objcgs() does redirect objcg->memcg to the parent on rmdir. An objcg of a dying child of root therefore passes every obj_cgroup_is_root() filter but resolves to the root memcg. Folios keep the objcg they were charged with, so this is easy to reach through zswap: allocate anon memory in a cgroup, move the task out, remove the cgroup, then write to the root cgroup's memory.reclaim. The reclaimed folios are charged through the reparented objcg and end up in refill_stock() with the root memcg: WARNING: mm/memcontrol.c:2198 at refill_stock+0x644/0x940 refill_stock+0x644/0x940 try_charge_memcg+0x12d6/0x1570 __obj_cgroup_charge+0x35/0xf0 obj_cgroup_charge+0x1de/0x210 obj_cgroup_charge_zswap+0x83/0x270 zswap_store+0x1620/0x2000 swap_writeout+0x94c/0x14c0 shrink_folio_list+0x3388/0x52b0 [...] try_to_free_mem_cgroup_pages+0x30d/0x830 user_proactive_reclaim+0x504/0x840 memory_reclaim+0x1f/0x30 Beyond the warning, the charge is asymmetric: obj_cgroup_uncharge_pages() skips refill_stock() for the root memcg, so the root's page counter grows and is never uncharged. It is not user visible, since memory.current is not exposed on the root, but it is a leak. Use try_charge(), which returns early for the root memcg, restoring the symmetry with obj_cgroup_uncharge_pages(). The above sequence was scripted into a standalone reproducer (zswap on, swap on a virtio disk, 512MB of anon memory faulted in inside a child of the root cgroup, the task then migrated to the root cgroup, the child removed, followed by "echo 600M swappiness=max > memory.reclaim" on the root) and run in a CONFIG_DEBUG_VM=y VM. It reproduces the splat on the first zswap store of a reparented folio, with the same call chain as the report. With this patch applied the splat is gone while the zswap store count over the run is unchanged, so the same path is still exercised. cgroup selftests test_zswap, test_kmem and test_memcontrol show no new failures.

CVSS Scores

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Meta Information

Published

2026-10-14

Last Modified

2026-10-19

Generated

2026-10-19

AI Q&A

2026-10-15

EPSS Evaluated

2026-10-18

NVD

CVE-2026-98414

EUVD

EUVD-2026-101063

Affected Vendors & Products

Vendor	Product	Version / Range
Linux	Linux	20d6c17252282c3af261d1cde8e34def1b2458c8
Linux	Linux	20d6c17252282c3af261d1cde8e34def1b2458c8
Linux	Linux	20d6c17252282c3af261d1cde8e34def1b2458c8
Linux	Linux	6.15

Helpful Resources

Exploitability

CWE

KEV

CWE ID	Description
CWE-UNKNOWN

Attack-Flow Graph

Executive Summary

This vulnerability in the Linux kernel involves incorrect memory charging in the memory controller (memcg). It occurs when an object cgroup (objcg) associated with a dying child cgroup incorrectly charges memory to the root memcg instead of the intended parent cgroup. This happens because objcg's memcg pointer isn't updated when the cgroup is removed, leading to asymmetric memory charging where the root memcg's counter grows without being uncharged.

Detection Guidance

This vulnerability is specific to the Linux kernel and may not have direct network detection methods. Monitor kernel logs for warnings like 'WARNING: mm/memcontrol.c:2198 at refill_stock+0x644/0x940' which indicate the issue. Check for asymmetric memory charges in root cgroup by examining memory.current and memory.usage_in_bytes under /sys/fs/cgroup/memory/

Impact Analysis

This vulnerability can cause memory leaks in the root cgroup's accounting, though it's not directly visible to users. It may lead to unexpected memory pressure or crashes in systems using zswap with memory cgroups. The impact is primarily on systems with active cgroup management and zswap enabled.

Compliance Impact

This vulnerability does not directly affect compliance with standards like GDPR or HIPAA as it involves a memory management issue in the Linux kernel. The impact is limited to potential memory leaks in the root memory cgroup, which does not expose user-visible counters or data exposure risks.

Mitigation Strategies

Apply the Linux kernel patch that modifies try_charge_memcg() to return early for root memcg. Update to a kernel version containing the fix. If immediate patching is not possible, disable zswap temporarily as it is a known attack vector for this vulnerability.

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