Bug 2513420 (CVE-2026-68288)

Summary: CVE-2026-68288 kernel: net: drop_monitor: fix info leak in NET_DM_ATTR_PAYLOAD
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security <prodsec-ir-bot>
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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's `drop_monitor` module. This vulnerability allows for information disclosure due to uninitialized padding bytes in the `NET_DM_ATTR_PAYLOAD` attribute. When the packet payload length is not a multiple of four, these uninitialized bytes are leaked to user space. A local attacker could exploit this to obtain sensitive kernel memory information.
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Description OSIDB Bzimport 2026-08-10 12:36:19 UTC 
In the Linux kernel, the following vulnerability has been resolved:

net: drop_monitor: fix info leak in NET_DM_ATTR_PAYLOAD

net_dm_packet_report_fill() and net_dm_hw_packet_report_fill() open code
the NET_DM_ATTR_PAYLOAD attribute to avoid zeroing the packet payload
before overwriting it with skb_copy_bits().

skb_put() reserves nla_total_size(payload_len), i.e. the header plus the
NLA_ALIGN() padding, but only payload_len bytes are copied in. When
payload_len is not a multiple of 4 the 1-3 padding bytes are never
initialized and are leaked to user space inside the netlink message.

KMSAN confirms the leak for the software path when the packet payload
length is not 4-byte aligned:

  BUG: KMSAN: kernel-infoleak in _copy_to_iter
   _copy_to_iter
   __skb_datagram_iter
   skb_copy_datagram_iter
   netlink_recvmsg
   sock_recvmsg
   __sys_recvfrom
  Uninit was created at:
   kmem_cache_alloc_node_noprof
   __alloc_skb
   net_dm_packet_work
  Bytes 173-175 of 176 are uninitialized

Use __nla_reserve(), which sets up the attribute header and zeroes the
padding, instead of open coding the attribute construction.
Comment 1 Mauro Matteo Cascella 2026-08-11 14:14:27 UTC 
Upstream advisory:
https://lore.kernel.org/linux-cve-announce/2026081027-CVE-2026-68288-da09@gregkh/T