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 19907.0.0

high Tenable Cloud Security Plugin ID 472177

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: ipv6: anycast: insert aca into global
hash under idev->lock syzbot reported a splat [1]: a slab-use-after-free in ipv6_chk_acast_addr(), which
walks the global inet6_acaddr_lst[] hash under RCU and dereferences a struct ifacaddr6 that has already
been freed while still linked in the hash, so a later reader walks into a dangling node. In
__ipv6_dev_ac_inc() the aca is allocated with refcount 1, then aca_get() bumps it to 2 to keep it alive
across the unlocked region. It is published to idev->ac_list under idev->lock, but ipv6_add_acaddr_hash()
runs after write_unlock_bh(). A concurrent teardown (ipv6_ac_destroy_dev() from addrconf_ifdown(), under
RTNL) can slip into that window: CPU0 __ipv6_dev_ac_inc CPU1 ipv6_ac_destroy_dev (RTNL)
------------------------------ ------------------------------------ aca_alloc() refcnt 1 aca_get() refcnt
2 write_lock_bh(idev->lock) add aca to ac_list write_unlock_bh(idev->lock) write_lock_bh(idev->lock) pull
aca off ac_list write_unlock_bh(idev->lock) ipv6_del_acaddr_hash(aca) hlist_del_init_rcu() is a no-op, aca
is not in the hash yet aca_put() refcnt 2->1 ipv6_add_acaddr_hash(aca) aca now inserted into the hash
aca_put() refcnt 1->0 call_rcu(aca_free_rcu) -> kfree(aca) The hash removal becomes a no-op because the
insertion has not happened yet, so once CPU0 inserts and drops the last reference, the aca is freed while
still linked in inet6_acaddr_lst[], and readers dereference freed memory after the slab slot is reused.
This window opened once RTNL stopped serializing the join path against device teardown. Move
ipv6_add_acaddr_hash() inside the idev->lock section so the ac_list and hash insertions are atomic with
respect to teardown: a racing remover now either misses the aca entirely or finds it in both lists.
acaddr_hash_lock is now nested under idev->lock, which is acquired in softirq context, so switch all
acaddr_hash_lock sites to spin_lock_bh() to avoid the irq lock inversion reported in [2]. [1]
https://syzkaller.appspot.com/bug?extid=a01df04303c131efbf3a [2]
https://lore.kernel.org/netdev/[email protected]/ (CVE-2026-53259)

Solution

Update the sys-kernel/cchost-kernel-6_18 library and its related packages to version 19907.0.0 or later.

Plugin Details

Severity: High

ID: 472177

Version: Revision 1.2

Type: Local

Family: Google COS Security Checks

Published: 10/3/2026

Updated: 10/3/2026

Supported Sensors: Tenable Cloud Security, Tenable Self-Hosted Container Security

Risk Information

VPR

Risk Factor: Medium

Score: 4.9

Percentile: 58.35

Vendor

Vendor Severity: HIGH

CVSS v2

Risk Factor: Medium

Base Score: 6.8

Temporal Score: 5

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

CVSS Score Source: CVE-2026-53259

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: 6/25/2026

Reference Information

CVE: CVE-2026-53259

Detections

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