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Vulnerabilities

Vulnerability · CVE-2026-81000

net: tun: bound receive headroom

Published Sep 11, 2026 · catalog updated Oct 27, 2026 · BSI

Last checked Oct 29, 2026. A connected source was read within the last 7 days.

Check if you run it

No confirmed exploitation is on record for CVE-2026-81000. EPSS is 0.36%. Act only if a listed version of BSI is installed.

Gaps on this record

  • No vendor fix or required action is stored. Compare the linked advisory before you change production.
Severity
High7.8
Known exploitation
Not in CISA/VulnCheck KEV
EPSS
0.36%
Remediation
Not established
Affected products
Linux Kernel

In the Linux kernel, the following vulnerability has been resolved: net: tun: bound receive headroom tun_get_user() uses tun->align both as skb headroom and when choosing how much packet data to keep linear. OVS can propagate an oversized headroom request from another port to TUN or TAP. When align is larger than the usable space in a one-page skb head, SKB_MAX_HEAD(align) underflows and the result becomes negative when stored in good_linear. That value later wraps when assigned to the size_t linear variable, and tun_alloc_skb() can place skb->data outside the allocated head. Bound the headroom stored by TUN to the one-page skb-head budget and the largest non-sentinel 16-bit skb header offset. Leave one linear byte for raw TUN and a complete Ethernet header for TAP, including NET_IP_ALIGN. Also pull the raw-TUN protocol byte and the TAP Ethernet header before accessing them, so these checks remain safe for nonlinear skbs supplied by other allocation paths.

Are you affected?

Enter the version you run. The result uses only the ranges stored on this record.

The check returns affected, not affected, or incomplete. It does not guess a version that is missing from the record.

  • Linux Kernel4.6.0 → 5.10.270; 5.11.0 → 5.15.221; 5.16.0 → 6.1.188

How to fix CVE-2026-81000

What to do

Three questions, each answered from this record only. Confirm the vendor advisory before you patch.

Should you patch?

No confirmed exploitation is on record for CVE-2026-81000. EPSS is 0.36%. Act only if a listed version of BSI is installed.

Which versions are affected?

Compare what you have installed with Kernel 4.6.0 → 5.10.270; 5.11.0 → 5.15.221; 5.16.0 → 6.1.188. Compare the installed version with the linked vendor advisory before you change production.

What should an analyst verify?

No weakness class is stored. EPSS 0.36%. There is no CISA KEV listing. No Exploit-DB or Metasploit reference is linked. Use the source links for the original advisory.

Code

The project this record applies to. Exploit listings stay in References.

Timeline

Detection, updates, and resolution for this record.

  1. Oct 26, 2026 · BSI CERT-Bund

    Detected

    CVE-2026-81000 is listed by Linux Kernel: Mehrere Schwachstellen.

  2. Oct 27, 2026 · OpenSSF OSV / OSV Scanner

    Fix available

    Kernel fixed in 5.10.270; Kernel fixed in 5.15.221; Kernel fixed in 6.1.188; Kernel fixed in 6.6.157

  3. Oct 27, 2026 · OpenSSF OSV / OSV Scanner

    Fix available

    Kernel fixed in 5.10.270; 5.11.0

  4. Oct 27, 2026 · OpenSSF OSV / OSV Scanner

    Updated

    In the Linux kernel, the following vulnerability has been resolved: net: tun: bound receive headroom tun_get_user() uses tun->align both as skb headroom and when choosing how much packet data to keep linear. OVS can propagate an oversized headroom request from another port to TUN or TAP. When align is larger than the usable space in a one-page skb head, SKB_MAX_HEAD(align) underflows and the resul

Sources

References

Freshness

Last verified in this catalog Oct 29, 2026. Significant claims (KEV, EPSS, CVSS, affected ranges) come from the source rows above — open the original publisher for the authoritative advisory.

  • OpenSSF OSV / OSV ScannerOct 28, 2026
  • CVE.orgOct 27, 2026
  • BSI CERT-BundOct 27, 2026