Google: sys-kernel/csql-kernel-6_1, sys-kernel/csql-kernel-6_6, sys-kernel/lakitu-kernel-6_1, sys-kernel/lakitu-kernel-6_6, sys-kernel/lakitu-nc-kernel-6_6, sys-kernel/lakitu-vgpu-kernel-6_6, sys-kernel/tpusev-kernel-6_6: security update to 18613.731.21

high Tenable Cloud Security Plugin ID 466357

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: inet: frags: strip GSO state from
fragments before reassembly A virtio_net_hdr (tun/tap, or AF_PACKET with PACKET_VNET_HDR) can mark an IPv4
or IPv6 fragment as GSO; nothing relates gso_type to frag_off.
inet_frag_reasm_prepare()/inet_frag_reasm_finish() keep the first fragment's skb as the head of the
reassembled datagram, including its shinfo->gso_size/gso_type/gso_segs, and chain the remaining fragments
on frag_list with whatever linear/paged layout they arrived with. After ip_defrag() (ip_local_deliver(),
nf_defrag_ipv4, ...) the reassembled skb therefore still claims to be GSO (SKB_GSO_DODGY), and the next
software segmentation point - udp_rcv_segment() on local delivery, validate_xmit_skb(), or the
ip_finish_output_gso() slow path - hands it to skb_segment(). skb_segment()'s frag_list walk assumes GRO-
shaped input and hits one of its BUG_ON()s. Two writes to a tap by an unprivileged user in its own userns
are enough: kernel BUG at net/core/skbuff.c:4899! Oops: invalid opcode: 0000 [#1] SMP KASAN NOPTI CPU: 0
UID: 1000 PID: 82 Comm: poc Not tainted 7.2.0-pentest+ #2 RIP: 0010:skb_segment+0x20ca/0x48b0 Call Trace:
<TASK> __udp_gso_segment+0x29a/0x27d0 udp4_ufo_fragment+0x458/0x6c0 inet_gso_segment+0x429/0x1340
skb_mac_gso_segment+0x233/0x4f0 __skb_gso_segment+0x308/0x660 udp_queue_rcv_skb+0x440/0xad0
udp_unicast_rcv_skb+0xc7/0x2c0 udp_rcv+0x16ce/0x2260 ip_protocol_deliver_rcu+0x197/0x2d0
ip_local_deliver+0x430/0x690 ip_rcv+0x16f/0x1f0 __netif_receive_skb_one_core+0x15e/0x1c0
__netif_receive_skb+0x1e/0x110 netif_receive_skb+0xf6/0x5c0 tun_rx_batched.isra.0+0x3ab/0x790
tun_get_user+0x17c3/0x3550 tun_chr_write_iter+0xba/0x1b0 vfs_write+0x646/0x1130 </TASK> Kernel panic - not
syncing: Fatal exception in interrupt This runs with BH disabled, so it is a panic rather than an oops.
The same is reachable with CAP_NET_RAW in a netns where a defrag point precedes a GSO point, and from a
guest whose VMM forwards virtio_net_hdr to a tap. The SKB_GSO_DODGY frag_list checks added by commit
3dcbdb134f32 ("net: gso: Fix skb_segment splat when splitting gso_size mangled skb having linear-headed
frag_list") and by commit 9e4b7a99a03a ("net: gso: fix panic on frag_list with mixed head alloc types") do
not cover it: page-backed heads skip them, and kmalloc heads skip them when gso_size == skb_headlen(head),
which the sender controls. An skb entering a frag queue is an IP fragment by definition and cannot
legitimately carry GSO state: GRO does not merge fragments and the stack segments before it fragments, so
only untrusted sources are affected. This has been reachable since commit f43798c27684 ("tun: Allow GSO
using virtio_net_hdr"), the first path that let userspace attach GSO metadata to an IP fragment. Reset the
GSO fields of every fragment as it is queued, in inet_frag_queue_insert(), which IPv4, IPv6,
nf_conntrack_reasm and 6lowpan reassembly share; then neither the head nor the frag_list members of the
reassembled skb carry them (the members matter too: the ip_do_fragment()/ip6_fragment() fast paths send
them out as they are). The head may remain CHECKSUM_PARTIAL; that is already accepted on receive and
resolved by skb_checksum_help() in ip_do_fragment()/ip6_fragment() on forward. Tested on top of net.git
(dc4b95b8fee9), x86_64: the tap reproducer above, two further IPv4 frag_list geometries that reach
BUG_ON(i >= nfrags) and BUG_ON(!list_skb->head_frag), and an IPv6 fragment-header variant
(udp6_ufo_fragment()) each panic the unpatched kernel; with this patch all four datagrams are delivered
intact and nothing is logged. (CVE-2026-80590)

Solution

Update the sys-kernel/csql-kernel-6_1 library and its related packages to version 18613.731.21 or later.

Plugin Details

Severity: High

ID: 466357

Version: Revision 1.1

Type: Local

Family: Google COS Security Checks

Published: 10/2/2026

Updated: 10/2/2026

Risk Information

VPR

Risk Factor: Low

Score: 3.3

Percentile: 50.58

Vendor

Vendor Severity: LOW

CVSS v2

Risk Factor: High

Base Score: 7.8

Temporal Score: 5.8

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

CVSS Score Source: CVE-2026-80590

CVSS v3

Risk Factor: High

Base Score: 8.6

Temporal Score: 7.5

Vector: CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/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: 8/28/2026

Reference Information

CVE: CVE-2026-80590

Detections

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