{"id":"CVE-2026-89555","aliases":[],"url":"https://o3.security/vulnerability/CVE-2026-89555","summary":"mpls: reload header after pskb_may_pull()","details":"In the Linux kernel, the following vulnerability has been resolved:\n\nmpls: reload header after pskb_may_pull()\n\nmpls_select_multipath() calls mpls_multipath_hash() to choose a nexthop\nwhen an MPLS route has multiple nexthops.  While walking the MPLS label\nstack, the hash routine caches hdr for the current label.  After finding\nthe bottom-of-stack label, it calls pskb_may_pull() before reading the\ninner IP header.\n\nIf an skb is constructed with the inner IP header in nonlinear data and\ninsufficient tailroom in the linear head, pskb_may_pull() calls\npskb_expand_head() to replace the skb head and free the old one.  This\nleaves hdr pointing to freed memory.  The IPv6 path can invalidate hdr\nagain when it performs a second pull for the larger header.\n\nThe issue was found through static analysis.  A reproducer sending a legal\nGeneve packet through a bareudp/MPLS multipath setup triggered the same\nKASAN report in 2 of 2 unpatched runs:\n\n  BUG: KASAN: slab-use-after-free in mpls_select_multipath\n  Read of size 1 at addr ffff88800ecc6e20 by task ksoftirqd/1/23\n\n  Call Trace:\n   mpls_select_multipath\n   mpls_forward\n   __netif_receive_skb_list_core\n   netif_receive_skb_list_internal\n   napi_complete_done\n   gro_cell_poll\n   __napi_poll\n   net_rx_action\n\n  Freed by task 23:\n   kfree\n   pskb_expand_head\n   __pskb_pull_tail\n   mpls_select_multipath\n\nReload hdr from the current skb head after each successful pull before\nderiving the inner IPv4 or IPv6 header pointer.","published":"2026-09-11T19:44:28.331Z","modified":"2026-09-14T03:46:15.581202611Z","cvss":{"score":9.8,"severity":"CRITICAL","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H"},"epss":null,"cisaKev":null,"exploitsKnown":null,"affectedPackages":[{"ecosystem":"Linux","name":"Kernel","fixedVersion":"6.12.109"}],"fix":null,"references":[{"type":"WEB","url":"https://git.kernel.org/stable/c/29e63b8d9fc150cc191b1c6eb7e16e1247e1b650"},{"type":"WEB","url":"https://git.kernel.org/stable/c/49d38c1b4390412f8950d33dfaee0ccbd17beb81"},{"type":"WEB","url":"https://git.kernel.org/stable/c/d82b90a38c2ca8a0694428eab0e9551c23f2447d"},{"type":"WEB","url":"https://git.kernel.org/stable/c/fed638a248116b8a249bd4202d28e5934bdc65ad"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/89xxx/CVE-2026-89555.json"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-89555"},{"type":"PACKAGE","url":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-09-14T03:46:15.581202611Z"}}