---
id: "CVE-2026-98853"
kind: "vulnerability"
aliases: ["CVE-2026-98853"]
title: "Linux kernel: unbounded IP-in-IP GSO nesting can exhaust the kernel stack"
severity: "unknown"
cvss: null
epss: null
exploited: false
status: "open"
category: "runtime"
products: []
ecosystems: []
tags: ["ip-tunnels", "kernel", "linux", "networking", "runtime"]
not_affected_if: ["no-ip-in-ip-tunnels"]
published_at: "2026-10-18T16:17:39+00:00"
first_seen_at: "2026-10-23T21:57:17+00:00"
updated_at: "2026-10-25T05:13:01+00:00"
sources: [{"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-98853", "first_seen_at": "2026-10-23T21:57:17+00:00"}]
---

# Linux kernel: unbounded IP-in-IP GSO nesting can exhaust the kernel stack

The Linux kernel's generic segmentation offload path re-entered the IPv4 and IPv6 segmentation handlers once per nested IP header without a depth limit, so a deeply nested packet can exhaust the kernel stack. The fix caps handler entries at the existing tunnel recursion limit and returns an error beyond it.

_Summary, check and fix written by a model from the sources; labelled as such._

## Fix

- Update the Linux kernel to a release that includes the upstream commit adding the recursion limit to net/core GSO handling (version unknown from the sources).

## Timeline

- 2026-10-23T21:57:17+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-98853

## From the sources

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.

---

_Free to read at a human pace. An API with keys and an MCP server are in preparation; early access: hello@infrastack.ai_