Cloudanix VulnDB

CVE-2026-98853

None

CVSS

—

EPSS

0.1%

Published

Oct 18, 2026

CISA due date

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Cloudanix analysis

Schedule a fix SSVC: Track

A Linux networking issue could let specially crafted traffic overwhelm system resources and cause crashes, though the chance of this happening in practice appears low.

Exploitation
Remote Unauthenticated
Attacker needs
None
Complexity
Moderate
Impact
Denial Of Service
Component
OS kernel
Class
Denial of service
Remediation
Upgrade
Effort
Medium
Patch risk
Low

What it actually does

Unbounded recursion in IPv4/IPv6 GSO handlers for deeply nested IP-in-IP packets exhausts the kernel stack because encap_level does not limit callback depth.

Why it matters to the business

Low-likelihood denial of service risk to Linux systems performing network segmentation, with minimal urgency indicated by stable low exploit probability and no known campaigns.

How an attack unfolds

An attacker sends crafted IP-in-IP encapsulated packets that trigger repeated entry into inet_gso_segment or ipv6_gso_segment; the absence of per-handler recursion counting allows the call stack to grow until a crash occurs.

How to fix it

Update the Linux kernel to a version containing the recursion limit enforcement that initializes a counter in skb_gso_cb and returns -EINVAL on the sixth entry using IP_TUNNEL_RECURSION_LIMIT.

How to confirm the fix worked

Confirm the presence of the skb_gso_cb counter initialization and the six-entry guard in inet_gso_segment and ipv6_gso_segment; test with a packet chain of six nesting levels to verify early return of -EINVAL.

Typical attack path

  1. Craft packets containing more than five levels of IP-in-IP encapsulation
  2. Route traffic through a GSO-enabled path such as IPIP, GRE, or UDP tunnels
  3. Trigger segmentation callbacks repeatedly until kernel stack exhaustion
  4. Cause system instability or crash

How to detect it

Review kernel logs for stack overflow oops involving gso_segment functions; inspect network traffic for unusually deep IP encapsulation chains that could trigger the vulnerable path.

What your security team should do

  • Track upstream kernel releases for the GSO recursion fix
  • Evaluate exposure in environments with heavy tunneling or virtualization workloads
  • Apply patches promptly once available given the five-day publication window

The record

In the Linux kernel, the following vulnerability has been resolved: net: gso: limit recursive IP-in-IP segmentation IP-in-IP GSO can re-enter inet_gso_segment() or ipv6_gso_segment() for each nested IP header. encap_level tracks header bytes, not callback depth, so a deep chain can exhaust the kernel stack. Making inet_gso_segment() stackable introduced unbounded IPv4 nesting; IPIP GSO/TSO later made the path reachable. The IPv6 stackable path was introduced separately and uses the same guard. Count IPv4 and IPv6 GSO handler entries in skb_gso_cb, initialized once per top-level GSO operation and preserved across GRE/UDP context changes. Use the existing IP_TUNNEL_RECURSION_LIMIT for both handlers. The first five entries pass, and the sixth returns -EINVAL before dispatching another GSO callback.

Affected packages

Ecosystem Package Introduced Fixed