Bug 2513451 (CVE-2026-68123) - CVE-2026-68123 kernel: openvswitch: fix GSO userspace truncation underflow
Summary: CVE-2026-68123 kernel: openvswitch: fix GSO userspace truncation underflow
Keywords:
Status: NEW
Alias: CVE-2026-68123
Product: Security Response
Classification: Other
Component: vulnerability
Version: unspecified
Hardware: All
OS: Linux
high
high
Target Milestone: ---
Assignee: Product Security
QA Contact:
URL:
Whiteboard:
Depends On:
Blocks:
TreeView+ depends on / blocked
 
Reported: 2026-08-10 12:38 UTC by OSIDB Bzimport
Modified: 2026-08-12 09:40 UTC (History)
2 users (show)

Fixed In Version:
Clone Of:
Environment:
Last Closed:
Embargoed:


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Description OSIDB Bzimport 2026-08-10 12:38:06 UTC
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.

Comment 1 Mauro Matteo Cascella 2026-08-11 11:42:22 UTC
Upstream advisory:
https://lore.kernel.org/linux-cve-announce/2026081056-CVE-2026-68123-49d8@gregkh/T


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