UBUNTU-CVE-2025-68800: Use After Free
In the Linux kernel, the following vulnerability has been resolved: mlxsw: spectrummr: Fix use-after-free when updating multicast route stats Cited commit added a dedicated mutex (instead of RTNL) to protect the multicast route list, so that it will not change while the driver periodically traverses it in order to update the kernel about multicast route stats that were queried from the device. One instance of list entry deletion (during route replace) was missed and it can result in a use-after-free [1]. Fix by acquiring the mutex before deleting the entry from the list and releasing it afterwards. [1] BUG: KASAN: slab-use-after-free in mlxswspmrstatsupdate+0x4a5/0x540 drivers/net/ethernet/mellanox/mlxsw/spectrummr.c:1006 [mlxswspectrum] Read of size 8 at addr ffff8881523c2fa8 by task kworker/2:5/22043 CPU: 2 UID: 0 PID: 22043 Comm: kworker/2:5 Not tainted 6.18.0-rc1-custom-g1a3d6d7cd014 #1 PREEMPT(full) Hardware name: Mellanox Technologies Ltd. MSN2010/SA002610, BIOS 5.6.5 08/24/2017 Workqueue: mlxswcore mlxswspmrstatsupdate [mlxswspectrum] Call Trace: <TASK> dumpstacklvl+0xba/0x110 printreport+0x174/0x4f5 kasanreport+0xdf/0x110 mlxswspmrstatsupdate+0x4a5/0x540 drivers/net/ethernet/mellanox/mlxsw/spectrummr.c:1006 [mlxswspectrum] processonework+0x9cc/0x18e0 workerthread+0x5df/0xe40 kthread+0x3b8/0x730 retfromfork+0x3e9/0x560 retfromforkasm+0x1a/0x30 </TASK> Allocated by task 29933: kasansavestack+0x30/0x50 kasansavetrack+0x14/0x30 kasankmalloc+0x8f/0xa0 mlxswspmrrouteadd+0xd8/0x4770 [mlxswspectrum] mlxswsprouterfibmreventwork+0x371/0xad0 drivers/net/ethernet/mellanox/mlxsw/spectrumrouter.c:7965 [mlxswspectrum] processonework+0x9cc/0x18e0 workerthread+0x5df/0xe40 kthread+0x3b8/0x730 retfromfork+0x3e9/0x560 retfromforkasm+0x1a/0x30 Freed by task 29933: kasansavestack+0x30/0x50 kasansavetrack+0x14/0x30 kasansavefreeinfo+0x3b/0x70 kasanslabfree+0x43/0x70 kfree+0x14e/0x700 mlxswspmrrouteadd+0x2dea/0x4770 drivers/net/ethernet/mellanox/mlxsw/spectrummr.c:444 [mlxswspectrum] mlxswsprouterfibmreventwork+0x371/0xad0 drivers/net/ethernet/mellanox/mlxsw/spectrumrouter.c:7965 [mlxswspectrum] processonework+0x9cc/0x18e0 workerthread+0x5df/0xe40 kthread+0x3b8/0x730 retfromfork+0x3e9/0x560 retfromforkasm+0x1a/0x30
Affected Software
Remediation
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ubuntu/linuxto a version that resolves this vulnerability.Fixed in 6.17.0-22.22 - Upgrade
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ubuntu/linux-riscvto a version that resolves this vulnerability.Fixed in 6.17.0-22.22.1 - Compensating control
In the mlxsw multicast-route list deletion path, acquire the dedicated mutex protecting the multicast route list before deleting the entry, then release the mutex after deletion.
Event History
Frequently Asked Questions
Which systems are most likely exposed to this issue?
Systems using the mlxsw Spectrum driver and multicast routing functionality are implicated. The provided crash report identifies Mellanox hardware and the mlxsw_spectrum module; the affected Ubuntu kernel package list includes linux, linux-realtime, linux-azure, linux-gcp, linux-azure-fde, linux-riscv, linux-gke, and linux-gkeop.
What condition triggers the use-after-free?
The issue occurs when a multicast route is replaced and its list entry is deleted while the driver’s periodic worker is traversing that list to update multicast route statistics. The missing mutex acquisition around deletion permits the worker to access an entry after it has been freed.
How can I identify signs that a system has already encountered the issue?
Look for KASAN slab-use-after-free reports in mlxsw_sp_mr_stats_update, referencing drivers/net/ethernet/mellanox/mlxsw/spectrum_mr.c. The supplied example shows the failure occurring in the mlxsw_core workqueue while running mlxsw_sp_mr_stats_update.