{"id":"CVE-2026-89555","title":"mpls: reload header after pskb_may_pull()","summary":"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 walk…","severity":"critical","cvss":9.8,"cvssVector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H","cvssSource":"cna","vendor":"Linux","product":"Linux","affected":["Linux >= 9f427a0e474a67b454420c131709600d44850486 < aa4fe0b450a461aa1162fe8375f5d28f4c957df8","Linux >= 9f427a0e474a67b454420c131709600d44850486 < b1c0783b2facc398437ad8f8b86c636d7a78f8db","Linux >= 9f427a0e474a67b454420c131709600d44850486 < bfaaff99238326166694354a63a76c02563f98b1","Linux >= 9f427a0e474a67b454420c131709600d44850486 < d9640239827d6d0cb84263b590f7a4f1596c17eb","Linux >= 9f427a0e474a67b454420c131709600d44850486 < fed638a248116b8a249bd4202d28e5934bdc65ad","Linux >= 9f427a0e474a67b454420c131709600d44850486 < d82b90a38c2ca8a0694428eab0e9551c23f2447d","Linux >= 9f427a0e474a67b454420c131709600d44850486 < 49d38c1b4390412f8950d33dfaee0ccbd17beb81","Linux >= 9f427a0e474a67b454420c131709600d44850486 < 29e63b8d9fc150cc191b1c6eb7e16e1247e1b650","Linux ad864d9fce0ec56cc8f6afe5c6a0e6d7f484b9eb","Linux >= 4.9.8 < 4.10","Linux 4.10"],"published":"2026-09-11","updated":"2026-09-14","sourceUpdated":"2026-09-14T12:00:57.921Z","source":"CVEORG","sourceUrl":"https://www.cve.org/CVERecord?id=CVE-2026-89555","references":[{"url":"https://git.kernel.org/stable/c/aa4fe0b450a461aa1162fe8375f5d28f4c957df8"},{"url":"https://git.kernel.org/stable/c/b1c0783b2facc398437ad8f8b86c636d7a78f8db"},{"url":"https://git.kernel.org/stable/c/bfaaff99238326166694354a63a76c02563f98b1"},{"url":"https://git.kernel.org/stable/c/d9640239827d6d0cb84263b590f7a4f1596c17eb"},{"url":"https://git.kernel.org/stable/c/fed638a248116b8a249bd4202d28e5934bdc65ad"},{"url":"https://git.kernel.org/stable/c/d82b90a38c2ca8a0694428eab0e9551c23f2447d"},{"url":"https://git.kernel.org/stable/c/49d38c1b4390412f8950d33dfaee0ccbd17beb81"},{"url":"https://git.kernel.org/stable/c/29e63b8d9fc150cc191b1c6eb7e16e1247e1b650"}],"tags":["cve.org"],"epss":0.00684,"epssPercentile":0.51172,"ingestedAt":"2026-09-14T15:23:07.451Z","slug":"CVE-2026-89555","body":"## Overview\n\nIn 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.\n\n## Affected\n\n- `Linux >= 9f427a0e474a67b454420c131709600d44850486 < aa4fe0b450a461aa1162fe8375f5d28f4c957df8`\n- `Linux >= 9f427a0e474a67b454420c131709600d44850486 < b1c0783b2facc398437ad8f8b86c636d7a78f8db`\n- `Linux >= 9f427a0e474a67b454420c131709600d44850486 < bfaaff99238326166694354a63a76c02563f98b1`\n- `Linux >= 9f427a0e474a67b454420c131709600d44850486 < d9640239827d6d0cb84263b590f7a4f1596c17eb`\n- `Linux >= 9f427a0e474a67b454420c131709600d44850486 < fed638a248116b8a249bd4202d28e5934bdc65ad`\n- `Linux >= 9f427a0e474a67b454420c131709600d44850486 < d82b90a38c2ca8a0694428eab0e9551c23f2447d`\n- `Linux >= 9f427a0e474a67b454420c131709600d44850486 < 49d38c1b4390412f8950d33dfaee0ccbd17beb81`\n- `Linux >= 9f427a0e474a67b454420c131709600d44850486 < 29e63b8d9fc150cc191b1c6eb7e16e1247e1b650`\n- `Linux ad864d9fce0ec56cc8f6afe5c6a0e6d7f484b9eb`\n- `Linux >= 4.9.8 < 4.10`\n- `Linux 4.10`\n\n## Remediation\n\nRefer to the linked advisories for vendor-supplied fixes and affected version ranges.","depth":"midnight","depthScore":54,"depthScoreParts":{"impact":53.9,"likelihood":0.1,"exploitation":0,"ransomware":0},"changes":[{"seq":183471,"id":"CVE-2026-89555","ts":1789356675501,"field":"cvss","old":"9.8","new":"5.9"},{"seq":183470,"id":"CVE-2026-89555","ts":1789356675501,"field":"severity","old":"critical","new":"medium"},{"seq":153364,"id":"CVE-2026-89555","ts":1789285350211,"field":"cvss","old":null,"new":"9.8"},{"seq":153363,"id":"CVE-2026-89555","ts":1789285350211,"field":"severity","old":"none","new":"critical"},{"seq":109614,"id":"CVE-2026-89555","ts":1789183732652,"field":"cvss","old":null,"new":"5.9"},{"seq":109613,"id":"CVE-2026-89555","ts":1789183732652,"field":"severity","old":"none","new":"medium"}]}