CVE-2026-68123: Linux kernel · openvswitch: fix GSO userspace truncation underflow
Affects Linux kernelSource CVE Database V5
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
- 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:HExploitation evidence
Disclosed: evidence found.
CVE published 10 Aug 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.
What to do
Upgrade to a fixed release listed under Affected software.
Affected software
| Product | Affected | Fixed in |
|---|---|---|
| LinuxLinux | Affected
| Fixed in
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| LinuxLinux | Affected
| Fixed in
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| LinuxLinux | Affected
| Fixed in
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| LinuxLinux | Affected
| Fixed in
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| LinuxLinux | Affected
| Fixed in
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| LinuxLinux | Affected
| Fixed in
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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
- git.kernel.org/stable/c/50a6a85f3d6b1d22d8436848606cdef5d2c490b4 (opens in a new tab)
- git.kernel.org/stable/c/2623c48cc3a8da9a1886fd8f65c0e348f4406fd6 (opens in a new tab)
- git.kernel.org/stable/c/e211b081901ffca76674082c73eeaed53524c369 (opens in a new tab)
- git.kernel.org/stable/c/a16eaaf7c0b0ccdef6166707d90ffbc6eebf6855 (opens in a new tab)
- git.kernel.org/stable/c/fbfa3ad2ad6f3a5624aba5211c46290fb98cc9dc (opens in a new tab)
- git.kernel.org/stable/c/100a23b1613e9218e0af654ef102352c713f0263 (opens in a new tab)
- git.kernel.org/stable/c/ea85dbcbe8d4056ecb54352f97743d138ea4c407 (opens in a new tab)
- git.kernel.org/stable/c/4032f8ed10fcb84d41c508dfb04be96589f78dfe (opens in a new tab)