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CVE-2026-89555

mpls: reload header after pskb_may_pull()

Published
Last modified
published
Not listed in CISA KEV
Fix
Fixed in 4.10, 5.10.270, 5.15.221, 6.1.188, 6.6.157, and 3 more
None on Exploit-DB, Metasploit or GitHub
  • Exploitation: none
  • Automatable: yes
  • Technical impact: total

Summary

In the Linux kernel, the following vulnerability has been resolved: mpls: reload header after pskb_may_pull() mpls_select_multipath() calls mpls_multipath_hash() 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 pskb_may_pull() 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, pskb_may_pull() calls pskb_expand_head() 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 mpls_select_multipath Read of size 1 at addr ffff88800ecc6e20 by task ksoftirqd/1/23 Call Trace: mpls_select_multipath mpls_forward __netif_receive_skb_list_core netif_receive_skb_list_internal napi_complete_done gro_cell_poll __napi_poll net_rx_action Freed by task 23: kfree pskb_expand_head __pskb_pull_tail mpls_select_multipath Reload hdr from the current skb head after each successful pull before deriving the inner IPv4 or IPv6 header pointer.

Timeline

  1. CVE published
  2. CISA SSVC assessment

    Exploitation: none · Automatable: yes · Technical impact: total

  3. Record last updated

Affected versions

  • Linux Linux

    From 9f427a0e474a67b454420c131709600d44850486 · fixed in aa4fe0b450a461aa1162fe8375f5d28f4c957df8; From 9f427a0e474a67b454420c131709600d44850486 · fixed in b1c0783b2facc398437ad8f8b86c636d7a78f8db; From 9f427a0e474a67b454420c131709600d44850486 · fixed in bfaaff99238326166694354a63a76c02563f98b1; From 9f427a0e474a67b454420c131709600d44850486 · fixed in d9640239827d6d0cb84263b590f7a4f1596c17eb; From 9f427a0e474a67b454420c131709600d44850486 · fixed in fed638a248116b8a249bd4202d28e5934bdc65ad; From 9f427a0e474a67b454420c131709600d44850486 · fixed in d82b90a38c2ca8a0694428eab0e9551c23f2447d; From 9f427a0e474a67b454420c131709600d44850486 · fixed in 49d38c1b4390412f8950d33dfaee0ccbd17beb81; From 9f427a0e474a67b454420c131709600d44850486 · fixed in 29e63b8d9fc150cc191b1c6eb7e16e1247e1b650; From 4.9.8 · fixed in 4.10

  • Linux Linux

    4.10

  • KernelLinux

    From 4.10.0 · fixed in 5.10.270; From 5.11.0 · fixed in 5.15.221; From 5.16.0 · fixed in 6.1.188; From 6.2.0 · fixed in 6.6.157; From 6.7.0 · fixed in 6.12.109; From 6.13.0 · fixed in 6.18.50; From 6.19.0 · fixed in 7.2.4

References 8

git.kernel.org