CVE-2026-72322: ipv6: mcast: Fix potential UAF in MLD delayed work
In the Linux kernel, the following vulnerability has been resolved:
ipv6: mcast: Fix potential UAF in MLD delayed work
A race condition exists between device teardown and incoming MLD query processing, leading to a Use-After-Free in the MLD delayed work.
During device destruction, the primary reference to inet6dev is dropped, which can drop its refcount to 0. The actual freeing of inet6dev memory is deferred via RCU.
Concurrently, the packet receive path runs under RCU read lock and obtains the inet6dev pointer. Because the memory is RCU-protected, CPU-0 can safely dereference inet6dev even if its refcount has hit 0.
However, if CPU-0 calls igmp6eventquery() and schedules delayed work, it attempts to acquire a reference using in6devhold(). This increments the refcount from 0 to 1, triggering a "refcountt: addition on 0" warning. Since the inet6dev memory is still scheduled to be freed after the RCU grace period, the device is freed while the work is still scheduled. When the work runs, it accesses the freed memory, causing a kernel panic.
Fix this by using refcountincnotzero() (via a new helper in6devholdsafe()) to prevent acquiring a reference if the device is already being destroyed. If the refcount is 0, we do not schedule the work.
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
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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/linuxto a version that resolves this vulnerability.Fixed in 6.8.0-147.147 - Upgrade
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ubuntu/linux-awsto a version that resolves this vulnerability.Fixed in 6.8.0-1067.70 - Upgrade
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ubuntu/linux-aws-7.0to a version that resolves this vulnerability.Fixed in 7.0.0-1013.13~24.04.1 - Upgrade
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ubuntu/linux-azureto a version that resolves this vulnerability.Fixed in 6.8.0-1071.79 - Upgrade
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ubuntu/linux-azure-fdeto a version that resolves this vulnerability.Fixed in 6.8.0-1069.76 - Upgrade
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ubuntu/linux-gcpto a version that resolves this vulnerability.Fixed in 6.8.0-1071.79 - Upgrade
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ubuntu/linux-gcp-7.0to a version that resolves this vulnerability.Fixed in 7.0.0-1013.13~24.04.1 - Upgrade
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ubuntu/linux-gketo a version that resolves this vulnerability.Fixed in 6.8.0-1066.74 - Upgrade
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ubuntu/linux-hwe-7.0to a version that resolves this vulnerability.Fixed in 7.0.0-34.34~24.04.1 - Upgrade
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ubuntu/linux-ibmto a version that resolves this vulnerability.Fixed in 6.8.0-1067.68 - Upgrade
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ubuntu/linux-lowlatencyto a version that resolves this vulnerability.Fixed in 6.8.0-147.147.1 - Upgrade
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ubuntu/linux-oracleto a version that resolves this vulnerability.Fixed in 6.8.0-1064.67 - Upgrade
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ubuntu/linux-oracle-7.0to a version that resolves this vulnerability.Fixed in 7.0.0-1012.12~24.04.1 - Upgrade
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ubuntu/linux-riscv-7.0to a version that resolves this vulnerability.Fixed in 7.0.0-34.34.1~24.04.1 - Upgrade
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ubuntu/linux-bluefieldto a version that resolves this vulnerability.Fixed in 6.8.0-1033.38 - Upgrade
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ubuntu/linux-realtimeto a version that resolves this vulnerability.Fixed in 6.8.1-1062.63 - Upgrade
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ubuntu/linux-aws-fipsto a version that resolves this vulnerability.Fixed in 6.8.0-1067.70+fips1 - Upgrade
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ubuntu/linux-azure-fipsto a version that resolves this vulnerability.Fixed in 6.8.0-1071.79+fips1 - Upgrade
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ubuntu/linux-fipsto a version that resolves this vulnerability.Fixed in 6.8.0-147.147+fips1 - Upgrade
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ubuntu/linux-gcp-fipsto a version that resolves this vulnerability.Fixed in 6.8.0-1071.79+fips1 - Upgrade
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ubuntu/linuxto a version that resolves this vulnerability.Fixed in 7.0.0-34.34 - Upgrade
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ubuntu/linux-awsto a version that resolves this vulnerability.Fixed in 7.0.0-1013.13 - Upgrade
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ubuntu/linux-azureto a version that resolves this vulnerability.Fixed in 7.0.0-1017.17 - Upgrade
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ubuntu/linux-azure-fdeto a version that resolves this vulnerability.Fixed in 7.0.0-1016.16 - Upgrade
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ubuntu/linux-gcpto a version that resolves this vulnerability.Fixed in 7.0.0-1013.13 - Upgrade
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ubuntu/linux-gketo a version that resolves this vulnerability.Fixed in 7.0.0-1007.8 - Upgrade
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ubuntu/linux-ibmto a version that resolves this vulnerability.Fixed in 7.0.0-1014.14 - Upgrade
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ubuntu/linux-oem-7.0to a version that resolves this vulnerability.Fixed in 7.0.0-1014.14 - Upgrade
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ubuntu/linux-oracleto a version that resolves this vulnerability.Fixed in 7.0.0-1012.12 - Upgrade
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ubuntu/linux-riscvto a version that resolves this vulnerability.Fixed in 7.0.0-34.34.1
Event History
Frequently Asked Questions
What is the severity of CVE-2026-72322?
CVE-2026-72322 has a risk score of 51, indicating a moderate severity vulnerability.
How do I fix CVE-2026-72322?
To fix CVE-2026-72322, ensure that your Linux kernel is updated to the latest version where this vulnerability has been patched.
What type of vulnerability is CVE-2026-72322?
CVE-2026-72322 is a Use After Free vulnerability caused by a race condition in the processing of MLD queries.
What component of the Linux kernel is affected by CVE-2026-72322?
CVE-2026-72322 affects the IPv6 multicast handling in the Linux kernel.
What can happen if CVE-2026-72322 is exploited?
Exploitation of CVE-2026-72322 may lead to an attacker gaining unauthorized access or causing system instability.