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VulnerabilityPublished Updated

CVE-2026-68123: Linux kernel · openvswitch: fix GSO userspace truncation underflow

Affects Linux kernelSource CVE Database V5

0

Not known to be exploited · CVSS 9.8 Critical · fixed in fbfa3ad2ad6f3a5624aba5211c46290fb98cc9dc : patch Linux kernel as a priority.

Data as of 26 Oct 2026, 12:42 UTC

CVSS 3.1 base score
9.8Critical
How severe the flaw is on the 0–10 CVSS scale.
EPSS
0.5% chance of exploitation in 30 days – higher than 45% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
CISA SSVC
Exploitation
No evidence of active exploitation and no public proof of concept
Automatable
Attackers can reliably automate steps 1–4 of the kill chain
Technical impact
Total control over the software or total information disclosure

CISA SSVC assessment, 2026-10-16.

Patch
Available – fixed in fbfa3ad2ad6f3a5624aba5211c46290fb98cc9dc, ea85dbcbe8d4056ecb54352f97743d138ea4c407, e211b081901ffca76674082c73eeaed53524c369 +5
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Exploitation evidence

  1. Disclosed: evidence found.

    CVE published 10 Aug 2026

  2. Detectable: no evidence on record.

    No public nuclei template indexed

  3. Weaponised: no evidence on record.

    No public exploit code indexed in Metasploit or Exploit-DB

  4. Exploited in the wild: no evidence on record.

    Not in CISA KEV and no source reports exploitation

  5. Observed by OffSeq 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.

What to do

Upgrade to a fixed release listed under Affected software.

Affected software

ProductAffectedFixed in
LinuxLinuxAffected
  • ≥ f2a4d086ed4c588d32fe9b7aa67fead7280e7bf1, < fbfa3ad2ad6f3a5624aba5211c46290fb98cc9dc
Fixed in
  • fbfa3ad2ad6f3a5624aba5211c46290fb98cc9dc
LinuxLinuxAffected
  • ≥ f2a4d086ed4c588d32fe9b7aa67fead7280e7bf1, < ea85dbcbe8d4056ecb54352f97743d138ea4c407
Fixed in
  • ea85dbcbe8d4056ecb54352f97743d138ea4c407
LinuxLinuxAffected
  • ≥ f2a4d086ed4c588d32fe9b7aa67fead7280e7bf1, < e211b081901ffca76674082c73eeaed53524c369
Fixed in
  • e211b081901ffca76674082c73eeaed53524c369
LinuxLinuxAffected
  • ≥ f2a4d086ed4c588d32fe9b7aa67fead7280e7bf1, < a16eaaf7c0b0ccdef6166707d90ffbc6eebf6855
Fixed in
  • a16eaaf7c0b0ccdef6166707d90ffbc6eebf6855
LinuxLinuxAffected
  • ≥ f2a4d086ed4c588d32fe9b7aa67fead7280e7bf1, < 4032f8ed10fcb84d41c508dfb04be96589f78dfe
Fixed in
  • 4032f8ed10fcb84d41c508dfb04be96589f78dfe
LinuxLinuxAffected
  • ≥ f2a4d086ed4c588d32fe9b7aa67fead7280e7bf1, < 2623c48cc3a8da9a1886fd8f65c0e348f4406fd6
Fixed in
  • 2623c48cc3a8da9a1886fd8f65c0e348f4406fd6

Description

In the Linux kernel, the following vulnerability has been resolved: openvswitch: fix GSO userspace truncation underflow OVS_ACTION_ATTR_TRUNC currently stores a delta from the original skb length in OVS_CB(skb)->cutlen. When a later userspace action segments a GSO skb, queue_gso_packets() reuses that delta for each smaller segment. A segment can then reach queue_userspace_packet() with cutlen greater than skb->len, underflowing the length passed to skb_zerocopy(). Store the maximum preserved length instead and bound each consumer against the current skb length. Use U32_MAX as the no-truncation sentinel so the value remains valid if skb geometry changes before a consumer handles it.

References

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