DEBIAN-CVE-2026-89555

In the Linux kernel, the following vulnerability has been resolved:  mpls: reload header after pskbmaypull()  mplsselectmultipath() calls mplsmultipathhash() to choose a nexthop when an MPLS route has multiple nexthops.  While walking the MPLS label stack, the hash routine caches hdr for the current label.  After finding the bottom-of-stack label, it calls pskbmaypull() before reading the inner IP header.  If an skb is constructed with the inner IP header in nonlinear data and insufficient tailroom in the linear head, pskbmaypull() calls pskbexpandhead() to replace the skb head and free the old one.  This leaves hdr pointing to freed memory.  The IPv6 path can invalidate hdr again when it performs a second pull for the larger header.  The issue was found through static analysis.  A reproducer sending a legal Geneve packet through a bareudp/MPLS multipath setup triggered the same KASAN report in 2 of 2 unpatched runs:    BUG: KASAN: slab-use-after-free in mplsselectmultipath   Read of size 1 at addr ffff88800ecc6e20 by task ksoftirqd/1/23    Call Trace:    mplsselectmultipath    mplsforward    netifreceiveskblistcore    netifreceiveskblistinternal    napicompletedone    grocellpoll    napipoll    netrxaction    Freed by task 23:    kfree    pskbexpandhead    _pskbpulltail    mplsselect_multipath  Reload hdr from the current skb head after each successful pull before deriving the inner IPv4 or IPv6 header pointer.