In the Linux kernel, the following vulnerability has been resolved:

xfrm: clear trailing padding in build_polexpire()

build_expire() clears the trailing padding bytes of struct
xfrm_user_expire after setting the hard field via memset_after(),
but the analogous function build_polexpire() does not do this for
struct xfrm_user_polexpire.

The padding bytes after the __u8 hard field are left
uninitialized from the heap allocation, and are then sent to
userspace via netlink multicast to XFRMNLGRP_EXPIRE listeners,
leaking kernel heap memory contents.

Add the missing memset_after() call, matching build_expire().

References

• https://nvd.nist.gov/vuln/detail/CVE-2026-31664
• https://git.kernel.org/stable/c/71a98248c63c535eaa4d4c22f099b68d902006d0
• https://git.kernel.org/stable/c/ac6985903db047eaff54db929e4bf6b06782788e
• https://git.kernel.org/stable/c/b1dfd6b27df35ef4f87825aa5f607378d23ff0f2
• https://git.kernel.org/stable/c/c221ed63a2769a0af8bd849dfe25740048f34ef4
• https://git.kernel.org/stable/c/e1af65c669ebb1666c54576614c01a7f9ffcfff6
• https://git.kernel.org/stable/c/eda30846ea54f8ed218468e5480c8305ca645e37