VulnerabilityPublished 18 Oct 2026

CVE-2026-98853: Linux kernel · net: gso: limit recursive IP-in-IP segmentation

Affects Linux kernelSource CVE Database V5

Not known to be exploited : upgrade to c949646c900e879afce47df1b607fa320eb63bf2 or 006c8b834aed8b02bd8fb9fb05e9e7ead37d1763 soon.

Data as of 26 Oct 2026, 13:47 UTC

Severity

High

Rated High by Threat Radar's AI analysis · CVSS not yet scored by NVD

EPSS: 0.1% chance of exploitation in 30 days – higher than 3% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch: Available – fixed in c949646c900e879afce47df1b607fa320eb63bf2, 006c8b834aed8b02bd8fb9fb05e9e7ead37d1763

Exploitation evidence

Disclosed: evidence found.
CVE published 18 Oct 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponised: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 26 Oct 2026.

Disclosed: The CVE record is public on cve.org. Its publication is t = 0.
Detectable: A public nuclei template can find exposed instances, for defenders and attackers alike.
Weaponised: Public exploit code exists in Metasploit or Exploit-DB, or CISA SSVC or the CVSS exploit maturity reports a public proof of concept.
Exploited in the wild: CISA KEV lists it, CISA SSVC rates exploitation active, or a source reports attacks.
Observed by OffSeq Mirage: OffSeq Mirage honeypot sensors recorded attack traffic for this CVE, or found exposed hosts without attack traffic.

Moments are spaced evenly, not to scale; a dashed line marks a gap of six months or more. Deltas count from t = 0. Sources that give only a date (CISA KEV, Exploit-DB, or a time of exactly 00:00Z) read “same day” rather than hours. Metasploit modules carry the flaw’s disclosure date, not their release date, and nuclei templates carry no date, so both appear above but not on the timeline.

What to do

Upgrade Linux kernel to c949646c900e879afce47df1b607fa320eb63bf2 or 006c8b834aed8b02bd8fb9fb05e9e7ead37d1763.

Affected software

Product	Affected	Fixed in
LinuxLinux	Affected ≥ 3347c960295583eee3fd58e5c539fb1972fbc005, < c949646c900e879afce47df1b607fa320eb63bf2	Fixed in c949646c900e879afce47df1b607fa320eb63bf2
LinuxLinux	Affected ≥ 3347c960295583eee3fd58e5c539fb1972fbc005, < 006c8b834aed8b02bd8fb9fb05e9e7ead37d1763	Fixed in 006c8b834aed8b02bd8fb9fb05e9e7ead37d1763
LinuxLinux	Affected =3.13	Fixed in–

AI-suggested

A fix is available in the Linux kernel commits identified by hashes c949646c900e879afce47df1b607fa320eb63bf2 and 006c8b834aed8b02bd8fb9fb05e9e7ead37d1763. Users should update to a Linux kernel version that includes these commits to remediate the vulnerability. No additional mitigation actions are specified or required.

Description

CVE-2026-98853 is a vulnerability in the Linux kernel's Generic Segmentation Offload (GSO) implementation for IP-in-IP packets. The flaw allows recursive IP-in-IP segmentation to re-enter segmentation functions for each nested IP header without proper depth tracking, potentially exhausting the kernel stack. The issue arises because the existing recursion guard tracks header bytes rather than callback depth, enabling unbounded IPv4 nesting. This vulnerability was addressed by counting GSO handler entries and enforcing a recursion limit to prevent excessive nesting.

Impact

This vulnerability could lead to kernel stack exhaustion due to unbounded recursive segmentation of nested IP-in-IP packets. Such stack exhaustion may cause denial of service or kernel instability. There is no indication of known exploitation in the wild. The impact is limited to affected Linux kernel versions with the vulnerable GSO implementation.

Summary

The Linux kernel's IP-in-IP GSO implementation could recursively re-enter inet_gso_segment() or ipv6_gso_segment() for each nested IP header due to improper recursion depth tracking. The encap_level variable tracked header bytes but not callback depth, allowing deep chains of nested IP headers to exhaust the kernel stack. This was introduced when inet_gso_segment() became stackable, enabling unbounded IPv4 nesting, and later made reachable via IPIP GSO/TSO. The fix involves counting IPv4 and IPv6 GSO handler entries in skb_gso_cb, initializing this count once per top-level GSO operation and preserving it across GRE/UDP context changes. The existing IP_TUNNEL_RECURSION_LIMIT is applied to both handlers, allowing five entries to pass and returning -EINVAL on the sixth to prevent further recursion.

References

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 26 Oct 2026, 09:42 UTC

Technical details

References

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