UBUNTU-CVE-2025-68801: Use After Free
In the Linux kernel, the following vulnerability has been resolved: mlxsw: spectrumrouter: Fix neighbour use-after-free We sometimes observe use-after-free when dereferencing a neighbour [1]. The problem seems to be that the driver stores a pointer to the neighbour, but without holding a reference on it. A reference is only taken when the neighbour is used by a nexthop. Fix by simplifying the reference counting scheme. Always take a reference when storing a neighbour pointer in a neighbour entry. Avoid taking a referencing when the neighbour is used by a nexthop as the neighbour entry associated with the nexthop already holds a reference. Tested by running the test that uncovered the problem over 300 times. Without this patch the problem was reproduced after a handful of iterations. [1] BUG: KASAN: slab-use-after-free in mlxswspneighentryupdate+0x2d4/0x310 Read of size 8 at addr ffff88817f8e3420 by task ip/3929 CPU: 3 UID: 0 PID: 3929 Comm: ip Not tainted 6.18.0-rc4-virtme-g36b21a067510 #3 PREEMPT(full) Hardware name: Nvidia SN5600/VMOD0013, BIOS 5.13 05/31/2023 Call Trace: <TASK> dumpstacklvl+0x6f/0xa0 printaddressdescription.constprop.0+0x6e/0x300 printreport+0xfc/0x1fb kasanreport+0xe4/0x110 mlxswspneighentryupdate+0x2d4/0x310 mlxswsprouterrifgonesync+0x35f/0x510 mlxswsprifdestroy+0x1ea/0x730 mlxswspinetaddrportvlanevent+0xa1/0x1b0 mlxswspinetaddrlagevent+0xcc/0x130 mlxswspinetaddrevent+0xf5/0x3c0 mlxswsprouternetdeviceevent+0x1015/0x1580 notifiercallchain+0xcc/0x150 callnetdevicenotifiersinfo+0x7e/0x100 netdevupperdevunlink+0x10b/0x210 netdevupperdevunlink+0x79/0xa0 vrfdelslave+0x18/0x50 dosetmaster+0x146/0x7d0 dosetlink.isra.0+0x9a0/0x2880 rtnlnewlink+0x637/0xb20 rtnetlinkrcvmsg+0x6fe/0xb90 netlinkrcvskb+0x123/0x380 netlinkunicast+0x4a3/0x770 netlinksendmsg+0x75b/0xc90 socksendmsg+0xbe/0x160 syssendmsg+0x5b2/0x7d0 syssendmsg+0xfd/0x180 syssendmsg+0x124/0x1c0 dosyscall64+0xbb/0xfd0 entrySYSCALL64afterhwframe+0x4b/0x53 [...] Allocated by task 109: kasansavestack+0x30/0x50 kasansavetrack+0x14/0x30 kasankmalloc+0x7b/0x90 kmallocnoprof+0x2c1/0x790 neighalloc+0x6af/0x8f0 neighcreate+0x63/0xe90 mlxswspnexthopneighinit+0x430/0x7e0 mlxswspnexthoptypeinit+0x212/0x960 mlxswspnexthop6groupinfoinit.constprop.0+0x81f/0x1280 mlxswspnexthop6groupget+0x392/0x6a0 mlxswspfib6entrycreate+0x46a/0xfd0 mlxswsprouterfib6replace+0x1ed/0x5f0 mlxswsprouterfib6eventwork+0x10a/0x2a0 processonework+0xd57/0x1390 workerthread+0x4d6/0xd40 kthread+0x355/0x5b0 retfromfork+0x1d4/0x270 retfromforkasm+0x11/0x20 Freed by task 154: kasansavestack+0x30/0x50 kasansavetrack+0x14/0x30 kasansavefreeinfo+0x3b/0x60 kasanslabfree+0x43/0x70 kmemcachefreebulk.part.0+0x1eb/0x5e0 kvfreercubulk+0x1f2/0x260 kfreercuwork+0x130/0x1b0 processonework+0xd57/0x1390 workerthread+0x4d6/0xd40 kthread+0x355/0x5b0 retfromfork+0x1d4/0x270 retfromforkasm+0x11/0x20 Last potentially related work creation: kasansavestack+0x30/0x50 kasanrecordauxstack+0x8c/0xa0 kvfreecallrcu+0x93/0x5b0 mlxswsprouterneigheventwork+0x67d/0x860 processonework+0xd57/0x1390 workerthread+0x4d6/0xd40 kthread+0x355/0x5b0 retfromfork+0x1d4/0x270 retfromforkasm+0x11/0x20
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
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ubuntu/linux-aws-5.15to a version that resolves this vulnerability.Fixed in 5.15.0-1103.110~20.04.1 - Upgrade
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ubuntu/linux-azure-5.15to a version that resolves this vulnerability.Fixed in 5.15.0-1110.119~20.04.1 - Upgrade
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ubuntu/linux-gcp-5.15to a version that resolves this vulnerability.Fixed in 5.15.0-1103.112~20.04.1 - Upgrade
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ubuntu/linux-awsto a version that resolves this vulnerability.Fixed in 5.15.0-1103.110 - Upgrade
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ubuntu/linux-aws-6.8to a version that resolves this vulnerability.Fixed in 6.8.0-1052.55~22.04.1 - Upgrade
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ubuntu/linux-azureto a version that resolves this vulnerability.Fixed in 5.15.0-1109.118 - Upgrade
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ubuntu/linux-azure-6.8to a version that resolves this vulnerability.Fixed in 6.8.0-1059.65~22.04.1 - Upgrade
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ubuntu/linux-azure-fdeto a version that resolves this vulnerability.Fixed in 5.15.0-1109.118.1 - Upgrade
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ubuntu/linux-gcpto a version that resolves this vulnerability.Fixed in 5.15.0-1103.112 - Upgrade
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ubuntu/linux-gcp-6.8to a version that resolves this vulnerability.Fixed in 6.8.0-1054.57~22.04.1 - Upgrade
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ubuntu/linux-gketo a version that resolves this vulnerability.Fixed in 5.15.0-1099.105 - Upgrade
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ubuntu/linux-ibmto a version that resolves this vulnerability.Fixed in 5.15.0-1097.100 - Upgrade
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ubuntu/linux-lowlatencyto a version that resolves this vulnerability.Fixed in 5.15.0-173.183 - Upgrade
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ubuntu/linux-nvidiato a version that resolves this vulnerability.Fixed in 5.15.0-1098.99 - Upgrade
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ubuntu/linux-raspito a version that resolves this vulnerability.Fixed in 5.15.0-1097.100 - Upgrade
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ubuntu/linuxto a version that resolves this vulnerability.Fixed in 6.8.0-110.110 - Upgrade
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ubuntu/linux-awsto a version that resolves this vulnerability.Fixed in 6.8.0-1052.55 - Upgrade
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ubuntu/linux-aws-6.17to a version that resolves this vulnerability.Fixed in 6.17.0-1012.12~24.04.1 - Upgrade
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ubuntu/linux-azureto a version that resolves this vulnerability.Fixed in 6.8.0-1054.60 - Upgrade
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ubuntu/linux-azure-6.17to a version that resolves this vulnerability.Fixed in 6.17.0-1013.13~24.04.1 - Upgrade
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ubuntu/linux-azure-fdeto a version that resolves this vulnerability.Fixed in 6.8.0-1058.65 - Upgrade
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ubuntu/linux-azure-nvidiato a version that resolves this vulnerability.Fixed in 6.8.0-1039.42 - Upgrade
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ubuntu/linux-gcpto a version that resolves this vulnerability.Fixed in 6.8.0-1054.57 - Upgrade
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ubuntu/linux-gcp-6.17to a version that resolves this vulnerability.Fixed in 6.17.0-1012.12~24.04.1 - Upgrade
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ubuntu/linux-gketo a version that resolves this vulnerability.Fixed in 6.8.0-1050.56 - Upgrade
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ubuntu/linux-gkeopto a version that resolves this vulnerability.Fixed in 6.8.0-1037.40 - Upgrade
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ubuntu/linux-hwe-6.17to a version that resolves this vulnerability.Fixed in 6.17.0-22.22~24.04.1 - Upgrade
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ubuntu/linux-ibmto a version that resolves this vulnerability.Fixed in 6.8.0-1051.51 - Upgrade
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ubuntu/linux-lowlatencyto a version that resolves this vulnerability.Fixed in 6.8.0-110.110.1 - Upgrade
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ubuntu/linux-nvidiato a version that resolves this vulnerability.Fixed in 6.8.0-1051.54 - Upgrade
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ubuntu/linux-nvidia-6.17to a version that resolves this vulnerability.Fixed in 6.17.0-1018.18 - Upgrade
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ubuntu/linux-nvidia-tegrato a version that resolves this vulnerability.Fixed in 6.8.0-1022.22 - Upgrade
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ubuntu/linux-oem-6.17to a version that resolves this vulnerability.Fixed in 6.17.0-1020.20 - Upgrade
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ubuntu/linux-oracleto a version that resolves this vulnerability.Fixed in 6.8.0-1049.50 - Upgrade
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ubuntu/linux-oracle-6.17to a version that resolves this vulnerability.Fixed in 6.17.0-1011.11~24.04.1 - Upgrade
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ubuntu/linux-raspito a version that resolves this vulnerability.Fixed in 6.8.0-1052.56 - Upgrade
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ubuntu/linux-riscv-6.17to a version that resolves this vulnerability.Fixed in 6.17.0-22.22.1~24.04.1 - Upgrade
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ubuntu/linux-xilinxto a version that resolves this vulnerability.Fixed in 6.8.0-1028.29 - Upgrade
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ubuntu/linux-bluefieldto a version that resolves this vulnerability.Fixed in 6.8.0-1017.21 - Upgrade
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ubuntu/linux-raspi-realtimeto a version that resolves this vulnerability.Fixed in 6.8.0-2042.43 - Upgrade
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ubuntu/linux-realtimeto a version that resolves this vulnerability.Fixed in 6.8.1-1047.48 - Upgrade
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ubuntu/linux-realtime-6.17to a version that resolves this vulnerability.Fixed in 6.17.0-1010.11~24.04.1 - Upgrade
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ubuntu/linux-aws-fipsto a version that resolves this vulnerability.Fixed in 6.8.0-1052.55+fips1 - Upgrade
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ubuntu/linux-azure-fipsto a version that resolves this vulnerability.Fixed in 6.8.0-1053.59+fips1 - Upgrade
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ubuntu/linux-fipsto a version that resolves this vulnerability.Fixed in 6.8.0-110.110+fips2 - Upgrade
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ubuntu/linux-gcp-fipsto a version that resolves this vulnerability.Fixed in 6.8.0-1054.57+fips1 - Upgrade
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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-awsto a version that resolves this vulnerability.Fixed in 6.17.0-1012.12 - Upgrade
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ubuntu/linux-azureto a version that resolves this vulnerability.Fixed in 6.17.0-1013.13 - Upgrade
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ubuntu/linux-gcpto a version that resolves this vulnerability.Fixed in 6.17.0-1012.12 - Upgrade
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ubuntu/linux-oracleto a version that resolves this vulnerability.Fixed in 6.17.0-1011.11 - Upgrade
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ubuntu/linux-raspito a version that resolves this vulnerability.Fixed in 6.17.0-1013.13 - Upgrade
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ubuntu/linux-realtimeto a version that resolves this vulnerability.Fixed in 6.17.0-1010.11 - Upgrade
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ubuntu/linux-riscvto a version that resolves this vulnerability.Fixed in 6.17.0-22.22.1 - Compensating control
Update the Linux kernel mlxsw spectrum_router neighbour handling so it always takes a reference when storing a neighbour pointer in a neighbour entry, while simplifying the reference-counting scheme to avoid redundant references for neighbours already referenced by nexthops.
Event History
Frequently Asked Questions
Which systems are most likely exposed to this issue?
The issue is in the mlxsw Spectrum router driver, so systems using that driver and its neighbour-handling paths are the relevant exposure set. The provided data identifies Ubuntu linux, linux-azure, linux-aws-fips, linux-azure-fips, linux-fips, linux-gcp-fips, linux-gcp, and linux-oracle packages.
What access does an attacker need to exploit this vulnerability?
The supplied vector indicates local access and low privileges are required, with no user interaction required. It also indicates high potential impact to confidentiality, integrity, and availability.
How can administrators identify signs that they may be affected?
A triggered issue may produce a KASAN slab use-after-free report in mlxsw_sp_neigh_entry_update. The example report shows the fault occurring during a read while the ip process was running.