VulnerabilityPublished 18 Oct 2026

CVE-2026-98554: Linux kernel · vlan: ensure sufficient headroom in vlan_dev_hard_header()

Source GCVE Database

Authoritative record:CVE-2026-98554· Medium

Not known to be exploited · fixed in cfba0f45553de2b803059e3d539a1e418df24da8 : update Linux kernel when convenient.

Data as of 26 Oct 2026, 17:16 UTC

Severity

Medium

Rated by Threat Radar · CVSS not yet scored by NVD

EPSS: 0.2% chance of exploitation in 30 days – higher than 11% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch: Available – fixed in cfba0f45553de2b803059e3d539a1e418df24da8, cd5dd68267c4238795fadaf02b3575ca3f8a6500, ca797491f0ae4bfde9039f79f6f1ed7781c9110f +5

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-xh57-3wrj-366f

What to do

Upgrade to a fixed release listed under Affected software.

Affected software

Product	Affected	Fixed in
LinuxLinux	Affected ≥ 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, < cfba0f45553de2b803059e3d539a1e418df24da8	Fixed in cfba0f45553de2b803059e3d539a1e418df24da8
LinuxLinux	Affected ≥ 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, < cd5dd68267c4238795fadaf02b3575ca3f8a6500	Fixed in cd5dd68267c4238795fadaf02b3575ca3f8a6500
LinuxLinux	Affected ≥ 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, < ca797491f0ae4bfde9039f79f6f1ed7781c9110f	Fixed in ca797491f0ae4bfde9039f79f6f1ed7781c9110f
LinuxLinux	Affected ≥ 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, < c7ee4bea64f559ea8e03260014775b64c720cb5b	Fixed in c7ee4bea64f559ea8e03260014775b64c720cb5b
LinuxLinux	Affected ≥ 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, < 90d51095371d96747f45bbd8504edf6513e039ef	Fixed in 90d51095371d96747f45bbd8504edf6513e039ef
LinuxLinux	Affected ≥ 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, < 55e007fc3b4d76fa4d6b4660f6904fe6ab045a1b	Fixed in 55e007fc3b4d76fa4d6b4660f6904fe6ab045a1b

AI-suggested

A fix has been implemented in the Linux kernel to address this vulnerability. Users should apply the official kernel updates that include this patch. Since this is a kernel-level fix, upgrading to the patched kernel version is the recommended remediation. Patch status is not explicitly stated in the provided data; users should consult the vendor or Linux kernel advisory for the exact fixed versions and update instructions.

Description

A vulnerability in the Linux kernel's VLAN handling was resolved by ensuring sufficient headroom in the vlan_dev_hard_header() function. The issue involved callers reserving insufficient headroom, which could trigger skb_under_panic() due to inadequate buffer space. The fix uses skb_cow_head() to guarantee enough headroom and applies concurrency-safe reads of device header length parameters to avoid race conditions during VLAN header processing.

Impact

The vulnerability could cause kernel panics (skb_under_panic()) due to insufficient buffer headroom during VLAN packet processing, potentially affecting system stability and reliability. There is no indication of remote code execution or privilege escalation. No known exploits in the wild have been reported.

Summary

The Linux kernel vulnerability (CVE-2026-98554) involved insufficient headroom in vlan_dev_hard_header() when callers reserved ETH_HLEN or less, or when skbs were allocated before dynamic device/headroom changes. This could cause skb_under_panic() due to buffer underrun. The patch introduced usage of skb_cow_head() when VLAN_FLAG_REORDER_HDR is not set to ensure sufficient headroom for VLAN and device headers. It also uses READ_ONCE() to safely read dev->hard_header_len and dev->needed_headroom, preventing concurrency issues during lockless transmit path execution. Additionally, it avoids LL_RESERVED_SPACE(dev) to prevent unnecessary reallocations on inner stacked VLAN devices after pushing the outer VLAN header.

References

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