Linux Distros Unpatched Vulnerability : CVE-2026-98852

critical Nessus Plugin ID 367096

Synopsis

The Linux/Unix host has one or more packages installed with a vulnerability that the vendor indicates will not be patched.

Description

The Linux/Unix host has one or more packages installed that are impacted by a vulnerability without a vendor supplied patch available.

- net: extend IPv6 exthdr detection of tunneled packets Commit c4336a07eb6b (net: correctly handle tunneled traffic on IPV6_CSUM GSO fallback) split skb_gso_has_extension_hdr() into mutually exclusive branches on skb->encapsulation. This did not yet address all paths: 1. With skb->encapsulation set, the outer header is not checked. IPv6 tunnels such as ip6_gre and ip6_tunnel add an outer Destination Options header by default (encap_limit). Their GSO packets skip software GSO, then skb_csum_hwoffload_help() sees the outer extension header and calls skb_checksum_help() on the GSO skb, which warns and drops it. 2. Tunnels over IPv6 without an outer transport header, such as ip6_tunnel, leave skb->transport_header at the inner transport header. skb_network_header_len() then spans the outer IPv6, tunnel and inner IP headers, a false positive. 3. UDP tunnels without an inner network header, such as SCTP-in-UDP or PSP, have no inner IPv6 header to check. Decide on the outer header alone. 4. Directly dereferencing inner_ip_hdr(skb)->version without skb_header_pointer() is unsafe. Instead, check ipv6_ext_hdr(nexthdr) on the outer IPv6 header and, if set, on the inner IPv6 header. Read the headers with skb_header_pointer(). Keep the skb_network_header_len() check when !skb->encapsulation to also catch encapsulated packets without skb->encapsulation (e.g., virtio). Use the same helper in skb_csum_hwoffload_help(). Its open coded test has the false positive of (2) and ignores the inner header. Background: checksum offload of tunneled packets invariants: Non-GSO skb: - If the inner packet is CHECKSUM_PARTIAL, Local Checksum Offload computes the outer checksum in software and the device offloads only the inner L4 checksum. - If the inner packet is CHECKSUM_NONE (e.g., SCTP-in-UDP, ESP-in-UDP, Remote Checksum Offload), the device offloads the outer UDP or GRE checksum instead. GSO skb: - A device with NETIF_F_GSO_UDP_TUNNEL_CSUM or NETIF_F_GSO_GRE_CSUM computes both inner and outer checksums per segment. The outer checksum is seeded with only the pseudo-header checksum. A NETIF_F_IPV6_CSUM device must parse through the outer headers to reach the inner ones. (CVE-2026-98852)

Note that Nessus relies on the presence of the package as reported by the vendor.

Solution

There is no known solution at this time.

Plugin Details

Severity: Critical

ID: 367096

File Name: unpatched_CVE_2026_98852.nasl

Version: 1.1

Type: Local

Agent: unix

Family: Misc.

Published: 10/18/2026

Updated: 10/18/2026

Supported Sensors: Frictionless Assessment Agent, Nessus Agent, Agentless Assessment, Tenable Cloud Security, Tenable Self-Hosted Container Security, Nessus

Risk Information

VPR

Risk Factor: Medium

Score: 4.9

Percentile: 58.42

CVSS v2

Risk Factor: High

Base Score: 7.5

Temporal Score: 6.4

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

CVSS Score Source: CVE-2026-98852

CVSS v3

Risk Factor: Critical

Base Score: 9.8

Temporal Score: 9

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

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

Vulnerability Information

CPE: cpe:/o:debian:debian_linux:12.0, p-cpe:/a:debian:debian_linux:linux

Required KB Items: Host/local_checks_enabled, Host/cpu, global_settings/vendor_unpatched, Host/OS/identifier

Exploit Ease: No known exploits are available

Vulnerability Publication Date: 10/18/2026

Reference Information

CVE: CVE-2026-98852

Detections

Analytics