Vulnerabilities

Vulnerability · CVE-2026-98954

net: always dissect GSO packets in __virtio_net_hdr_to_skb()

Published Oct 23, 2026 · catalog updated Oct 25, 2026 · net: always dissect GSO

Last checked Nov 6, 2026. A connected source was read within the last 7 days.

Check if you run it

No confirmed exploitation is on record for CVE-2026-98954. EPSS is 0.17%. Act only if a listed version of net: always dissect GSO is installed.

Severity

Unknown—

Known exploitation

Not in CISA/VulnCheck KEV

EPSS

0.17%

Remediation

Advisory link

Affected products

Linux Kernel

In the Linux kernel, the following vulnerability has been resolved: net: always dissect GSO packets in __virtio_net_hdr_to_skb() Commit 9e8db5913264 ("net: avoid false positives in untrusted gso validation") added a '&& skb->network_header' check before flow-dissecting GSO packets without VIRTIO_NET_HDR_F_NEEDS_CSUM in __virtio_net_hdr_to_skb(), because some callers (such as tun_get_user(), tun_xdp_one(), virtnet_receive_done(), and raw_verify_header()) called virtio_net_hdr_*_to_skb() before initializing skb->network_header and skb->dev. Because __alloc_skb() and __build_skb_around() zero-initialize skb->network_header to 0 (unlike mac_header and transport_header which are initialized to ~0U), those four callers always had skb->network_header == 0 and bypassed flow dissection in __virtio_net_hdr_to_skb(). More generally, skb->network_header is an offset from skb->head (where 0 is also a valid offset whenever skb_headroom(skb) is 0), not a boolean flag. Whenever the 'if (gso_type && skb->network_header)' branch was skipped, the fallback 'else if (gso_type)' only pulled nh_min_len + thlen (40 bytes for TCPv4) without dissecting the packet, without validating ip_proto or n_proto, and without setting skb->transport_header. If the packet has a malformed network header, it is not rejected and a subsequent skb_probe_transport_header() also fails, leaving skb->transport_header at ~0U (0xffff). Similarly, if an IPv4 packet carries IP options (ihl > 5) or an IPv6 packet carries extension headers, pulling only nh_min_len + thlen can leave the TCP header outside skb->head. In both cases, tcp_hdrlen(skb) in skb_gso_transport_seglen() reads out-of-bounds: BUG: KASAN: slab-out-of-bounds in skb_gso_transport_seglen Read of size 2 by task poc/133 skb_gso_transport_seglen (net/core/gso.c:155) skb_gso_validate_mac_len (net/core/gso.c:270) tbf_enqueue (net/sched/sch_tbf.c:260) dev_qdisc_enqueue (net/core/dev.c:4227) __dev_queue_xmit (net/core/dev.c:4884) In addition, checking virtio_n