CVE-2026-68169
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/
CSIRTS triage
- What
- Use-after-free vulnerability in MPTCP path manager userspace handling when retrieving local IDs.
- Who is affected
- Systems running affected Linux kernel versions with MPTCP enabled.
- Urgency
- Medium priority; not currently exploited but memory corruption could lead to denial of service or code execution.
- Action
- Apply kernel security patch when available from your Linux distribution.
AI-assisted analysis generated from the source advisory — verify against the original.
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Exploitation outlook
- Low exploitation risk0.21% 30-day exploitation probability — currently an unlikely target, but scores change as exploit code circulates. Riskier than 10% of all EPSS-scored CVEs.
Advisory coverage (3)
- unknownDSA-6466-1 linux - security updatedebian · 2026-08-25
- mediumCVE-2026-68169: mptcp: pm: userspace: fix use-after-free in get_local_idmsrc · 2026-08-11
- unknownCVE-2026-68169: In the Linux kernel, the following vulnerability has been resolved: mptcp: pm: userspace: fix …nvd · 2026-08-10
External references
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