Riskcovery

CVE-2026-68169

mptcp: pm: userspace: fix use-after-free in get_local_id

State
Published
Severity
Not scored
Published
Aug 10, 2026
Updated
Aug 23, 2026
Reserved
Jul 30, 2026

Read the record on cve.org

Description

In the Linux kernel, the following vulnerability has been resolved:

mptcp: pm: userspace: fix use-after-free in get_local_id

In mptcp_pm_userspace_get_local_id(), the address entry is looked up under spinlock, but its id is read after dropping the lock. A concurrent deletion can free the entry between the unlock and the read, leading to UAF.

The race window is narrow. It was reproduced only with a locally constructed stress test that repeatedly overlaps an MP_JOIN SYN with a MPTCP_PM_CMD_SUBFLOW_DESTROY request.

However, the KASAN report below confirms that the race is reachable:

[ 666.319376] BUG: KASAN: slab-use-after-free in mptcp_userspace_pm_get_local_id+0x1dc/0x1f0 [ 666.319386] Read of size 1 at addr ffff888124845610 by task swapper/0/0 ... [ 666.319401] Call Trace: [ 666.319405] <IRQ> [ 666.319408] dump_stack_lvl+0x53/0x70 [ 666.319412] print_address_description.constprop.0+0x2c/0x3b0 [ 666.319418] print_report+0xbe/0x2b0 [ 666.319421] ? mptcp_userspace_pm_get_local_id+0x1dc/0x1f0 [ 666.319423] kasan_report+0xce/0x100 [ 666.319426] ? mptcp_userspace_pm_get_local_id+0x1dc/0x1f0 [ 666.319429] mptcp_userspace_pm_get_local_id+0x1dc/0x1f0 [ 666.319433] mptcp_pm_get_local_id+0x371/0x440 ... [ 666.319821] Allocated by task 45539: [ 666.319844] kasan_save_stack+0x33/0x60 [ 666.319855] kasan_save_track+0x14/0x30 [ 666.319858] __kasan_kmalloc+0x8f/0xa0 [ 666.319863] __kmalloc_noprof+0x1e7/0x520 [ 666.319867] sock_kmalloc+0xdf/0x130 [ 666.319885] sock_kmemdup+0x1b/0x40 [ 666.319888] mptcp_userspace_pm_append_new_local_addr+0x261/0x500 [ 666.319910] mptcp_pm_nl_announce_doit+0x16a/0x610 ... [ 666.319967] Freed by task 45560: [ 666.319988] kasan_save_stack+0x33/0x60 [ 666.319991] kasan_save_track+0x14/0x30 [ 666.319994] kasan_save_free_info+0x3b/0x60 [ 666.319998] __kasan_slab_free+0x43/0x70 [ 666.320000] kfree+0x166/0x440 [ 666.320003] sock_kfree_s+0x1d/0x50 [ 666.320007] mptcp_userspace_pm_delete_local_addr.isra.0+0x157/0x200 [ 666.320011] mptcp_pm_nl_subflow_destroy_doit+0x51d/0xea0

Fix by copying the id into a local variable while still holding the lock, and use -1 as a "not found" sentinel.

Scores

The record has no CVSS score.

Weaknesses

The record names no weakness.

Affected Products

ProductVersions
LinuxLinux
  • e373bfc8ec3d6496ec7e11dd7f4d087a44b1009a to before 8ce48d2879aafc0e7a6f8bfc3613c0ba979ec6f5Affected
  • ed34dfa19ddbd1e4c85a73636f8cba0211025ea4 to before d2c3760b45f2f481a4dd4c5adef4a29dfabd948fAffected
  • f012d796a6de662692159c539689e47e662853a8 to before 31ce5af66891f79998fb2e8b8df08e3c98fd72e3Affected
  • f012d796a6de662692159c539689e47e662853a8 to before d64f6c02495f3fad674038cfa7ec049671b59e7bAffected
  • f012d796a6de662692159c539689e47e662853a8 to before 40dde4b5d98279471a70e5c8bb713182738c00d9Affected
  • f012d796a6de662692159c539689e47e662853a8 to before 9bc6d5e4ca9f3cbb41d43400b3a31cb0403796c9Affected
  • 005a3ad289eb604216dcaa03646de36cb08624a0Affected
  • 6.1.79 to before 6.1.184Affected
  • 6.6.18 to before 6.6.151Affected
  • 6.7.6 to before 6.8Affected
LinuxLinux
  • 6.8Affected
  • before 6.8Not affected
  • 6.1.184 through 6.1.*Not affected
  • 6.6.151 through 6.6.*Not affected
  • 6.12.103 through 6.12.*Not affected
  • 6.18.42 through 6.18.*Not affected
  • 7.1.6 through 7.1.*Not affected
  • 7.2 and laterNot affected

References

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