Linux kernel skb_zerocopy sharedfrag flag omission enables writeup
CVE-2026-99284 Published on November 7, 2026
net: skbuff: propagate shared-frag marker in skb_zerocopy()
In the Linux kernel, the following vulnerability has been resolved:
net: skbuff: propagate shared-frag marker in skb_zerocopy()
skb_zerocopy() moves frag descriptors from @from into @to and takes a
reference on each frag, but it does not copy skb_shinfo(from)->flags into
skb_shinfo(to)->flags. A destination skb holding the same page-cache
backed frags as the source therefore reports skb_has_shared_frag() as
false.
That breaks the invariant relied on by later in-place writers. ESP input
checks skb_has_shared_frag() before deciding whether an uncloned
nonlinear skb can skip skb_cow_data(); with the marker lost, an skb that
skb_zerocopy() built for nfnetlink_queue or for an openvswitch upcall is
decrypted in place, letting an unprivileged user write into the page
cache of a root-owned read-only file.
Propagate SKBFL_SHARED_FRAG when frag descriptors are copied, as done for
the other frag-transfer helpers.
Products Associated with CVE-2026-99284
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Affected Versions
Linux:- Version af2806f8f90a150160be898cd85332459c83c5cb and below 1c623e3cbf43f12dd4a72712079bfa247a9b8ba3 is affected.
- Version af2806f8f90a150160be898cd85332459c83c5cb and below d7d6ff98d5d1b400f02211f962ac32cc0020aeab is affected.
- Version af2806f8f90a150160be898cd85332459c83c5cb and below 1a9c180cd8435917b7516edfb1c9148032c28773 is affected.
- Version af2806f8f90a150160be898cd85332459c83c5cb and below 79dc34beb1fdb3da79753e51e15c68591a2561fe is affected.
- Version 3.14 is affected.
- Before 3.14 is unaffected.
- Version 6.18.61, <= 6.18.* is unaffected.
- Version 7.2.15, <= 7.2.* is unaffected.
- Version 7.3.2, <= 7.3.* is unaffected.
- Version 7.4-rc1, <= * is unaffected.