Bug 2546529 (CVE-2026-98239) - CVE-2026-98239 kernel: net: lan743x: fix RX checksum use-after-free
Summary: CVE-2026-98239 kernel: net: lan743x: fix RX checksum use-after-free
Keywords:
Status: NEW
Alias: CVE-2026-98239
Product: Security Response
Classification: Other
Component: vulnerability
Version: unspecified
Hardware: All
OS: Linux
medium
medium
Target Milestone: ---
Assignee: Product Security DevOps Team
QA Contact:
URL:
Whiteboard:
Depends On:
Blocks:
TreeView+ depends on / blocked
 
Reported: 2026-10-06 09:39 UTC by OSIDB Bzimport
Modified: 2026-10-09 06:58 UTC (History)
17 users (show)

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


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Description OSIDB Bzimport 2026-10-06 09:39:16 UTC
In the Linux kernel, the following vulnerability has been resolved:

net: lan743x: fix RX checksum use-after-free

lan743x_rx_process_buffer() adds each non-first receive buffer to the
head skb's frag_list.  On the last descriptor, lan743x_rx_trim_skb()
linearizes the head and frees the fragment skb metadata.

The checksum-success path then writes ip_summed through the local skb
pointer, which still points to the final fragment.  This causes a
use-after-free write when a packet spans more than one receive buffer.

Set ip_summed on the surviving head skb instead.  Multi-buffer receive
can occur after a live MTU increase because existing ring entries keep
their old buffer size until they are replenished.

A KUnit test invoking lan743x_rx_process_buffer() with a two-buffer
packet produced a one-byte KASAN use-after-free write before this change.
The same test passed after the change.  The driver object also builds
with W=1.  This was not tested on physical LAN743x hardware.


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