UBUNTU-CVE-2026-74660: Use After Free
In the Linux kernel, the following vulnerability has been resolved: netfilter: ebtnflog: pin the NFLOG backend nflogunregister() runs after the per-net teardown so its final RCU grace period also drains readers that obtained the logger from a per-net binding. However, ebtnflog passes an explicit ULOG log type to nflogpacket() without holding a reference on the selected logger module, unlike the xtNFLOG and nftlog frontends. An ebtables nflog rule can therefore remain callable while nfnetlinklog is unloaded. The resulting interleaving is: CPU 0 CPU 1 nfnetlinklogfini() unregisterpernetsubsys() kfree(nfnllogpernet(net)) ebtnflogtg() nflogpacket() nfulnllogpacket() instancelookupgetrcu() The global ULOG logger is still registered at this point, so CPU 1 dereferences the per-net state after CPU 0 has freed it. KASAN reported: BUG: KASAN: slab-use-after-free in instancelookupgetrcu Read of size 8 at addr ff110001052e6210 by task poc/92 Call Trace: instancelookupgetrcu+0x1ce/0x1f0 [nfnetlinklog] nfulnllogpacket+0x248/0x2fb0 [nfnetlinklog] nflogpacket+0x204/0x300 ebtnflogtg+0x351/0x550 ebtdotable+0xedf/0x22b0 Allocated by task 90: kmallocnoprof+0x186/0x470 opsinit+0x6d/0x420 registerpernetoperations+0x2f6/0x670 registerpernetsubsys+0x23/0x40 Freed by task 93: kfree+0x131/0x3c0 opsundolist+0x3e3/0x700 unregisterpernetoperations+0x232/0x490 unregisterpernetsubsys+0x1c/0x30 nfnetlinklogfini+0x34/0x450 [nfnetlinklog] Acquire the ULOG logger module reference when an ebtnflog rule is validated and release it when the rule is destroyed. Request the NFLOG backend for legacy callers when needed, matching xtNFLOG. This prevents module teardown until all ebtnflog rules have stopped using the logger.
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 5.15.0-1117.124~20.04.1 - Upgrade
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ubuntu/linux-azure-5.15to a version that resolves this vulnerability.Fixed in 5.15.0-1123.132~20.04.1 - Upgrade
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ubuntu/linux-azure-fde-5.15to a version that resolves this vulnerability.Fixed in 5.15.0-1122.131~20.04.1 - Upgrade
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ubuntu/linux-gcp-5.15to a version that resolves this vulnerability.Fixed in 5.15.0-1118.128~20.04.1 - Upgrade
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ubuntu/linux-hwe-5.15to a version that resolves this vulnerability.Fixed in 5.15.0-198.208~20.04.1 - Upgrade
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ubuntu/linux-ibm-5.15to a version that resolves this vulnerability.Fixed in 5.15.0-1111.115~20.04.1 - Upgrade
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ubuntu/linux-intel-iotg-5.15to a version that resolves this vulnerability.Fixed in 5.15.0-1112.118~20.04.1 - Upgrade
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ubuntu/linux-lowlatency-hwe-5.15to a version that resolves this vulnerability.Fixed in 5.15.0-195.205~20.04.1 - Upgrade
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ubuntu/linux-oracle-5.15to a version that resolves this vulnerability.Fixed in 5.15.0-1114.120~20.04.1 - Upgrade
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ubuntu/linux-riscv-5.15to a version that resolves this vulnerability.Fixed in 5.15.0-1111.115~20.04.1 - Upgrade
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ubuntu/linuxto a version that resolves this vulnerability.Fixed in 5.15.0-198.208 - Upgrade
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ubuntu/linux-awsto a version that resolves this vulnerability.Fixed in 5.15.0-1117.124 - Upgrade
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ubuntu/linux-azureto a version that resolves this vulnerability.Fixed in 5.15.0-1123.132 - Upgrade
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ubuntu/linux-azure-fdeto a version that resolves this vulnerability.Fixed in 5.15.0-1122.131 - Upgrade
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ubuntu/linux-gcpto a version that resolves this vulnerability.Fixed in 5.15.0-1118.128 - Upgrade
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ubuntu/linux-gketo a version that resolves this vulnerability.Fixed in 5.15.0-1113.119 - Upgrade
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ubuntu/linux-gkeopto a version that resolves this vulnerability.Fixed in 5.15.0-1100.108 - Upgrade
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ubuntu/linux-ibmto a version that resolves this vulnerability.Fixed in 5.15.0-1111.115 - Upgrade
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ubuntu/linux-intel-iotgto a version that resolves this vulnerability.Fixed in 5.15.0-1112.118 - Upgrade
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ubuntu/linux-kvmto a version that resolves this vulnerability.Fixed in 5.15.0-1109.114 - Upgrade
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ubuntu/linux-lowlatencyto a version that resolves this vulnerability.Fixed in 5.15.0-195.205 - Upgrade
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ubuntu/linux-nvidiato a version that resolves this vulnerability.Fixed in 5.15.0-1112.113 - Upgrade
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ubuntu/linux-oracleto a version that resolves this vulnerability.Fixed in 5.15.0-1114.120 - Upgrade
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ubuntu/linux-xilinx-zynqmpto a version that resolves this vulnerability.Fixed in 5.15.0-1080.84 - Upgrade
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ubuntu/linux-bluefieldto a version that resolves this vulnerability.Fixed in 5.15.0-1101.103 - Upgrade
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ubuntu/linux-intel-iot-realtimeto a version that resolves this vulnerability.Fixed in 5.15.0-1109.111 - Upgrade
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ubuntu/linux-realtimeto a version that resolves this vulnerability.Fixed in 5.15.0-1116.125 - Upgrade
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ubuntu/linux-aws-fipsto a version that resolves this vulnerability.Fixed in 5.15.0-1117.124+fips1 - Upgrade
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ubuntu/linux-azure-fipsto a version that resolves this vulnerability.Fixed in 5.15.0-1123.132+fips1 - Upgrade
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ubuntu/linux-fipsto a version that resolves this vulnerability.Fixed in 5.15.0-198.208+fips1 - Upgrade
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ubuntu/linux-gcp-fipsto a version that resolves this vulnerability.Fixed in 5.15.0-1118.128+fips1 - Upgrade
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ubuntu/linux-nvidia-tegrato a version that resolves this vulnerability.Fixed in 6.8.0-1036.39
Event History
Frequently Asked Questions
What conditions are required to trigger this issue?
An ebtables NFLOG rule must be callable while the nfnetlink_log backend is being unloaded. The vulnerable path occurs because ebt_nflog invokes logging without holding a reference to the selected logger module.
What is the likely impact if the issue is exploited?
The race causes a use-after-free when the logging path dereferences freed per-network namespace state. The reported severity vector indicates that confidentiality, integrity, and availability may all be affected.
Is this exploitable remotely?
The provided severity vector lists local attack vector, low attack complexity, low privileges required, and no user interaction. The supplied information does not establish a remote exploitation path.
Which Ubuntu kernel packages are listed as affected?
The listed software includes ubuntu/linux, ubuntu/linux-azure, ubuntu/linux-aws-fips, ubuntu/linux-azure-fips, ubuntu/linux-fips, ubuntu/linux-gcp-fips, ubuntu/linux-gcp, and ubuntu/linux-oracle.