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    <link>https://vulnerability.circl.lu</link>
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    <lastBuildDate>Thu, 01 Oct 2026 22:59:18 +0000</lastBuildDate>
    <item>
      <title>CVE-2026-53392 — NFSv4/flexfiles: reject zero filehandle version count</title>
      <link>https://vulnerability.circl.lu/vuln/cve-2026-53392</link>
      <description>&lt;p&gt;&lt;strong&gt;Affected:&lt;/strong&gt; Linux&lt;/p&gt;
&lt;p&gt;In the Linux kernel, the following vulnerability has been resolved:&lt;/p&gt;
&lt;p&gt;NFSv4/flexfiles: reject zero filehandle version count&lt;/p&gt;
&lt;p&gt;ff_layout_alloc_lseg() decodes the filehandle-version array count
from the flexfiles layout body. The value is used as the count for
kzalloc_objs(), and the current code only rejects NULL.&lt;/p&gt;
&lt;p&gt;A zero count yields ZERO_SIZE_PTR, which can be stored in
dss_info-&amp;gt;fh_versions even though later flexfiles paths assume that at
least one filehandle version exists.&lt;/p&gt;
&lt;p&gt;Reject fh_count == 0 before the allocation, matching the existing zero
version_count validation in the flexfiles GETDEVICEINFO parser.&lt;/p&gt;
&lt;p&gt;A QEMU/KASAN run with a malformed flexfiles layout hit:&lt;/p&gt;
&lt;p&gt;KASAN: null-ptr-deref in range [0x0000000000000010-0x0000000000000017]
  RIP: 0010:ff_layout_encode_ff_layoutupdate.isra.0+0x15f/0x750
  ff_layout_encode_layoutreturn+0x683/0x970
  nfs4_xdr_enc_layoutreturn+0x278/0x3a0
  Kernel panic - not syncing: Fatal exception&lt;/p&gt;
&lt;p&gt;The patched kernel rejects the malformed layout without KASAN/oops/panic,
and a valid fh_count=1 regression still opens, reads, and unmounts cleanly.&lt;/p&gt;</description>
      <content:encoded>&lt;p&gt;&lt;strong&gt;Affected:&lt;/strong&gt; Linux&lt;/p&gt;
&lt;p&gt;In the Linux kernel, the following vulnerability has been resolved:&lt;/p&gt;
&lt;p&gt;NFSv4/flexfiles: reject zero filehandle version count&lt;/p&gt;
&lt;p&gt;ff_layout_alloc_lseg() decodes the filehandle-version array count
from the flexfiles layout body. The value is used as the count for
kzalloc_objs(), and the current code only rejects NULL.&lt;/p&gt;
&lt;p&gt;A zero count yields ZERO_SIZE_PTR, which can be stored in
dss_info-&amp;gt;fh_versions even though later flexfiles paths assume that at
least one filehandle version exists.&lt;/p&gt;
&lt;p&gt;Reject fh_count == 0 before the allocation, matching the existing zero
version_count validation in the flexfiles GETDEVICEINFO parser.&lt;/p&gt;
&lt;p&gt;A QEMU/KASAN run with a malformed flexfiles layout hit:&lt;/p&gt;
&lt;p&gt;KASAN: null-ptr-deref in range [0x0000000000000010-0x0000000000000017]
  RIP: 0010:ff_layout_encode_ff_layoutupdate.isra.0+0x15f/0x750
  ff_layout_encode_layoutreturn+0x683/0x970
  nfs4_xdr_enc_layoutreturn+0x278/0x3a0
  Kernel panic - not syncing: Fatal exception&lt;/p&gt;
&lt;p&gt;The patched kernel rejects the malformed layout without KASAN/oops/panic,
and a valid fh_count=1 regression still opens, reads, and unmounts cleanly.&lt;/p&gt;</content:encoded>
      <guid isPermaLink="false">https://vulnerability.circl.lu/vuln/cve-2026-53392</guid>
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