Bug 2492333 (CVE-2026-53014)

Summary: CVE-2026-53014 kernel: net/sched: act_mirred: fix wrong device for mac_header_xmit check in tcf_blockcast_redir
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
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Priority: medium    
Version: unspecifiedCC: rhel-process-autobot, watson-tool-maintainers
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Hardware: All   
OS: Linux   
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A flaw was found in the Linux kernel. When the kernel's traffic control (TC) subsystem processes network packets for redirection across different types of network devices, it can incorrectly handle packet headers. This can lead to corruption of network packet data. A local attacker could potentially exploit this to cause the system to crash, resulting in a denial of service (DoS).
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Description OSIDB Bzimport 2026-06-24 18:06:19 UTC 
In the Linux kernel, the following vulnerability has been resolved:

net/sched: act_mirred: fix wrong device for mac_header_xmit check in tcf_blockcast_redir

In tcf_blockcast_redir(), when iterating block ports to redirect
packets to multiple devices, the mac_header_xmit flag is queried
from the wrong device. The loop sends to dev_prev but queries
dev_is_mac_header_xmit(dev) — which is the NEXT device in the
iteration, not the one being sent to.

This causes tcf_mirred_to_dev() to make incorrect decisions about
whether to push or pull the MAC header. When the block contains
mixed device types (e.g., an ethernet veth and a tunnel device),
intermediate devices get the wrong mac_header_xmit flag, leading to
skb header corruption. In the worst case, skb_push_rcsum with an
incorrect mac_len can exhaust headroom and panic.

The last device in the loop is handled correctly (line 365-366 uses
dev_is_mac_header_xmit(dev_prev)), confirming this is a copy-paste
oversight for the intermediate devices.

Fix by using dev_prev instead of dev for the mac_header_xmit query,
consistent with the device actually being sent to.
Comment 1 Keith Grant 2026-06-25 19:02:06 UTC 
Upstream advisory:
https://lore.kernel.org/linux-cve-announce/2026062450-CVE-2026-53014-3438@gregkh/T