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Vulnerabilities/CVE-2026-63993Public Intelligence Dossier
Source: linux · Limited verification•Last verified: •Collection Running
CVE-2026-63993Unknown / EvaluatingCRITICAL (raw)CVSS 9.8CWE-416

In the Linux kernel, the following vulnerability has been resolved: vxlan: do not reuse cached ip_hdr() value after skb_tunnel_check_pmtu() skb_tunnel_check_pmtu() can change skb->head

Published: 19 Jul 2026•Last updated: 16 Oct 2026, 09:49 PM IST•Source identifier: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
Dossier completeness: source-provided sections 2 / 3 · rule guidance available. Missing source facts count as incomplete.
Official source
CISA KEV catalog
Unknown
KEV status was not determined.
CVSS score
9.8CRITICAL (raw)
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Metric source416baaa9-dc9f-4396-8d5f-8c081fb06d67
EPSS probability
0.5%0.005
Percentile43rd
Weakness type
CWE-416
No further CWE recorded
Remediation
Patch status unknown
No fixed version or KB recorded

Why It Matters

Analysis dossier

Why It Matters

In the Linux kernel, the following vulnerability has been resolved: vxlan: do not reuse cached ip_hdr() value after skb_tunnel_check_pmtu() skb_tunnel_check_pmtu() can change skb->head. Reusing old_iph afer skb_tunnel_check_pmtu() can cause an UAF. Use instead ip_hdr(skb) as done in drivers/net/bareudp.c and drivers/net/geneve.c. Found by Sashiko.

SOC priority

High Severity / Review

Actively exploited

Unknown

Publicly disclosed

Unknown

Risk basis: SOC ecosystem technology relevance; CRITICAL severity; Critical CVSS without confirmed KEV exploitation

Affected Products & Remediation

1 source-backed product
Affected products and versions (source)
  • linux linux kernel · >= 5.9 < 5.10.259; >= 5.11 < 5.15.210; >= 5.16 < 6.1.176; >= 6.2 < 6.6.143; >= 6.7 < 6.12.93; >= 6.13 < 6.18.35; >= 6.19 < 7.0.12; 7.1 · NVD CPE · Source
Recorded patch / KBNot provided by source

Vendor or catalog guidance (source)

Not provided by source

Known exploitation (source facts)

Only what a source states. Unknown means no source has said either way; it is not "not exploited".

CISA KEV
Unknown
Exploited (source statement)
Unknown
Publicly disclosed (source)
Unknown

Suggested hunting (rule-based inference)

SecOps Signal recommendation (rule-based inference). These steps are hunting hypotheses from the vulnerability class; they do not state or imply that exploitation occurred here or anywhere.

Matched network-unauthenticated (CVSS AV:N, CVSS PR:N, CVSS UI:N)

Exposure

  1. Identify devices reporting this CVE and note which expose the affected service to untrusted networks.Telemetry: DeviceTvmSoftwareVulnerabilities · A network-reachable, no-privilege vector makes internet-facing instances the first exposure question. · Rule network-unauthenticated

Exploitation evidence

  1. Review inbound connections to the affected service from unexpected sources since the advisory date.Telemetry: DeviceNetworkEvents · Hunting hypothesis from the CVSS vector; it does not show that exploitation occurred. · Rule network-unauthenticated

Response

  1. Confirm the source-stated update is installed and the CVE is no longer reported.Telemetry: DeviceTvmSoftwareVulnerabilities · A follow-up inventory check verifies remediation. · Rule network-unauthenticated

CISA KEV Record

CISA KEV status was not determined for this record.

Change History & Source Data

— No recorded material change

CNA / source
416baaa9-dc9f-4396-8d5f-8c081fb06d67
Record status · verification
UPDATED · NVD API
CPE
cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*, cpe:2.3:o:linux:linux_kernel:7.1:rc1:*:*:*:*:*:*, cpe:2.3:o:linux:linux_kernel:7.1:rc2:*:*:*:*:*:*, cpe:2.3:o:linux:linux_kernel:7.1:rc3:*:*:*:*:*:*, cpe:2.3:o:linux:linux_kernel:7.1:rc4:*:*:*:*:*:*, cpe:2.3:o:linux:linux_kernel:7.1:rc5:*:*:*:*:*:*

Evidence & Provenance

3 public sources
git.kernel.orgSource recordnvd.nist.govSource recordgit.kernel.orgSource record

Linked by the query's stored exact CVE association. Review required tables and validation status before use.

Detection Hunting Query
Target: DeviceTvmSoftwareVulnerabilities•Defender XDR
Detect endpoints exposed to CVE-2026-63993
Purpose: Exposure assessment (Category: Exposure Check)Why linked: Query metadata names CVE-2026-63993
DeviceTvmSoftwareVulnerabilities| where CveId == "CVE-2026-63993"| project DeviceId, DeviceName, OSPlatform, OSVersion, SoftwareVendor, SoftwareName, SoftwareVersion, CveId, VulnerabilitySeverityLevel, RecommendedSecurityUpdate, RecommendedSecurityUpdateId| sort by VulnerabilitySeverityLevel desc
Schema Checked · Not runtime validatedSource: SecOps Signal deterministic template · Limited verificationStatic screening: Passed structure and schema checks; tenant execution is not verified.
Open KQL Library

Correlated briefings

— No published briefing references this CVE

SecOps Signal surfaces public advisory facts only. A missing value means the source has not published it, not that your environment is unaffected. No tenant inventory is connected.