CVE-2026-53366: Linux IPv4 Paged Alloc Frag Size Miscalc Bug
CVE-2026-53366 Published on July 16, 2026
ipv4: account for fraggap on the paged allocation path
In the Linux kernel, the following vulnerability has been resolved:
ipv4: account for fraggap on the paged allocation path
In __ip_append_data(), when the paged-allocation branch is taken,
alloclen and pagedlen are computed as
alloclen = fragheaderlen + transhdrlen;
pagedlen = datalen - transhdrlen;
datalen already includes fraggap, but the fraggap bytes carried over
from the previous skb are copied into the new skb's linear area at
offset transhdrlen by the subsequent skb_copy_and_csum_bits(). The
linear area is therefore undersized by fraggap bytes while pagedlen is
overstated by the same amount.
The non-paged branch sets alloclen to fraglen, which already accounts
for fraggap because datalen does. Bring the paged branch in line by
adding fraggap to alloclen and subtracting it from pagedlen.
After this adjustment, copy no longer collapses to -fraggap on the
paged path, so remove the stale comment describing that old arithmetic.
Products Associated with CVE-2026-53366
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Affected Versions
Linux:- Version 8eb77cc73977d88787b37c92831b1c242e035396 and below ce494707a9c07f27c219ca67f3e138061f53d9b3 is affected.
- Version 8eb77cc73977d88787b37c92831b1c242e035396 and below a9c24eda24bd15f432e37824e6fc440977cb241c is affected.
- Version 8eb77cc73977d88787b37c92831b1c242e035396 and below 77798d7be6ef71e72fb6fc8a2901bf74ebc9706f is affected.
- Version 8eb77cc73977d88787b37c92831b1c242e035396 and below c04d9ece23deb9e26c19f9ca215e98b3295aa1bb is affected.
- Version 8eb77cc73977d88787b37c92831b1c242e035396 and below eca856950f7cb1a221e02b99d758409f2c5cec42 is affected.
- Version 6.0 is affected.
- Before 6.0 is unaffected.
- Version 6.6.144, <= 6.6.* is unaffected.
- Version 6.12.95, <= 6.12.* is unaffected.
- Version 6.18.38, <= 6.18.* is unaffected.
- Version 7.1.3, <= 7.1.* is unaffected.
- Version 7.2-rc1, <= * is unaffected.