CVE-2026-68123 openvswitch: fix GSO userspace truncation underflow
An integer underflow in the Linux kernel's Open vSwitch module can cause a denial of service when processing GSO packets with truncation actions.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-68123?
CVE-2026-68123 is a critical vulnerability in Linux, published on 10 Aug 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official 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.
Weakness: CWE-191
Which versions are affected by CVE-2026-68123?
How do I fix CVE-2026-68123?
Apply the vendor's patch.
Is CVE-2026-68123 being exploited?
There is no known exploitation of CVE-2026-68123 in the wild and no public exploit code.
Sources
Also known as BELL-CVE-2026-68123, DEBIAN-CVE-2026-68123, GHSA-wf82-h5xg-m662, UBUNTU-CVE-2026-68123.