Bug 2461482 (CVE-2026-31664)

Summary: CVE-2026-31664 kernel: xfrm: clear trailing padding in build_polexpire()
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security <prodsec-ir-bot>
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Priority: low    
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 xfrm subsystem. This vulnerability arises because the `build_polexpire()` function does not clear trailing padding bytes within the `xfrm_user_polexpire` structure. Consequently, these uninitialized padding bytes, which contain kernel heap memory contents, are sent to userspace via netlink multicast. A local attacker could exploit this to disclose potentially sensitive information from kernel memory.
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Description OSIDB Bzimport 2026-04-24 15:04:05 UTC 
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().
Comment 1 Keith Grant 2026-04-24 22:25:30 UTC 
Upstream advisory:
https://lore.kernel.org/linux-cve-announce/2026042405-CVE-2026-31664-d315@gregkh/T