VulnerabilityPublished 18 Oct 2026

CVE-2026-98568: Linux kernel · vxlan: use one headroom snapshot for neighbour replies

Source GCVE Database

Authoritative record:CVE-2026-98568· High

Not known to be exploited · fixed in ff022fd9d0f0282c575e11778b96bd1b637503eb : patch Linux kernel soon.

Data as of 26 Oct 2026, 17:16 UTC

Severity

High

Rated by Threat Radar · CVSS not yet scored by NVD

EPSS: 0.2% chance of exploitation in 30 days – higher than 9% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch: Available – fixed in ff022fd9d0f0282c575e11778b96bd1b637503eb, a3c5eb6e382dd426a5e7eb08608897ed57167ff7, 481506a756dcd828ef42391cb08f38d8d96d38fc +4

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.

ghsa-489c-q3cc-mm5r

What to do

Upgrade to a fixed release listed under Affected software.

Affected software

Product	Affected	Fixed in
LinuxLinux	Affected >=3.12.18 <3.13 >=3.13.10 <3.14	Fixed in ff022fd9d0f0282c575e11778b96bd1b637503eb a3c5eb6e382dd426a5e7eb08608897ed57167ff7 481506a756dcd828ef42391cb08f38d8d96d38fc 315d42ca39f69846662961c25dcf2bb07c350d14 45a67662bf8ce3aa5643accf98d328dfbb47eaf6 3.14 3.13
LinuxLinux	Affected =3.14	Fixed in–

AI-suggested

A fix has been implemented in the Linux kernel to address this vulnerability by snapshotting the headroom once and using that value consistently. Users should update to the patched kernel version containing this fix. Since no specific patch links or vendor advisories are provided, users should consult their Linux distribution's security updates for the official fix.

Description

A time-of-check to time-of-use (TOCTOU) race condition was identified and resolved in the Linux kernel's VXLAN implementation. The vulnerability occurs because vxlan_na_create() samples the headroom size twice, allowing a concurrent vxlan_changelink() to modify the headroom between reads. This can cause an out-of-bounds write when the Ethernet header is written, potentially leading to memory corruption. The issue was detected by KASAN during testing and has been fixed by snapshotting the headroom once for allocation and reservation.

Impact

This vulnerability can cause out-of-bounds memory writes in the kernel, which may lead to memory corruption, system instability, or potential escalation of privileges if exploited. However, there is no indication of known exploits in the wild. The issue affects the integrity and stability of the Linux kernel networking stack.

Summary

The Linux kernel VXLAN module had a TOCTOU race condition in vxlan_na_create() where the function sampled LL_RESERVED_SPACE() twice to size and reserve headroom for neighbour replies. A concurrent vxlan_changelink() could update needed_headroom between these reads, causing the second sampled value to exceed the allocated buffer size. This led to an out-of-bounds write of the Ethernet header. The race was reproducible and detected by KASAN. The fix involves taking a single snapshot of the headroom value and using it consistently for allocation and reservation to prevent the race.

References

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