Google: sys-kernel/cchost-kernel-6_18, sys-kernel/csql-kernel-6_18, sys-kernel/lakitu-kernel-6_18, sys-kernel/lakitu-nc-kernel-6_18: security update to 19999.44.126

high Tenable Cloud Security Plugin ID 475215

Description

There are packages installed that are affected by a vulnerability referenced in the following CVE:

- 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.
(CVE-2026-98414)

Solution

Update the sys-kernel/cchost-kernel-6_18 library and its related packages to version 19999.44.126 or later.

Plugin Details

Severity: High

ID: 475215

Version: Revision 1.1

Type: Local

Family: Google COS Security Checks

Published: 10/16/2026

Updated: 10/16/2026

Risk Information

VPR

Risk Factor: Medium

Score: 4.9

Percentile: 58.42

Vendor

Vendor Severity: LOW

CVSS v2

Risk Factor: High

Base Score: 7.2

Temporal Score: 5.3

Vector: CVSS2#AV:L/AC:L/Au:N/C:C/I:C/A:C

CVSS Score Source: CVE-2026-98414

CVSS v3

Risk Factor: High

Base Score: 7.8

Temporal Score: 6.8

Vector: CVSS:3.0/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

Temporal Vector: CVSS:3.0/E:U/RL:O/RC:C

Vulnerability Information

Exploit Ease: No known exploits are available

Vulnerability Publication Date: 10/14/2026

Reference Information

CVE: CVE-2026-98414

Detections

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