UBUNTU-CVE-2026-72482: Use After Free
In the Linux kernel, the following vulnerability has been resolved: gpib: fix double decrement of descriptorbusy in commandioctl() commit d1857f8296dc ("gpib: fix use-after-free in IO ioctl handlers") introduced a descriptorbusy reference counter to pin struct gpibdescriptor across IO ioctl operations. In commandioctl(), the error path inside the loop decrements descriptorbusy and breaks, but execution then falls through to the unconditional decrement after the loop, underflowing the counter to -1. This re-enables the use-after-free that the original fix was meant to prevent: a concurrent closedevioctl() sees descriptorbusy == 0 on an actively-used descriptor and frees it. Remove the early decrement from the error path. The post-loop decrement already handles all exit paths, matching the correct pattern used in readioctl() and writeioctl().
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Upgrade
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ubuntu/linux-aws-7.0to a version that resolves this vulnerability.Fixed in 7.0.0-1014.14~24.04.1 - Upgrade
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ubuntu/linux-azure-7.0to a version that resolves this vulnerability.Fixed in 7.0.0-1017.17~24.04.1 - Upgrade
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ubuntu/linux-azure-fde-7.0to a version that resolves this vulnerability.Fixed in 7.0.0-1016.16~24.04.1 - Upgrade
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ubuntu/linux-gcp-7.0to a version that resolves this vulnerability.Fixed in 7.0.0-1014.14~24.04.1 - Upgrade
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ubuntu/linux-hwe-7.0to a version that resolves this vulnerability.Fixed in 7.0.0-38.38~24.04.4 - Upgrade
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ubuntu/linux-nvidia-7.0to a version that resolves this vulnerability.Fixed in 7.0.0-1024.25~24.04.1 - Upgrade
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ubuntu/linux-oracle-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-riscv-7.0to a version that resolves this vulnerability.Fixed in 7.0.0-38.38.1~24.04.1 - Upgrade
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ubuntu/linuxto a version that resolves this vulnerability.Fixed in 7.0.0-38.38 - Upgrade
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ubuntu/linux-awsto a version that resolves this vulnerability.Fixed in 7.0.0-1014.14 - 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 7.0.0-1014.14 - Upgrade
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ubuntu/linux-gketo a version that resolves this vulnerability.Fixed in 7.0.0-1008.9 - Upgrade
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ubuntu/linux-ibmto a version that resolves this vulnerability.Fixed in 7.0.0-1015.15 - Upgrade
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ubuntu/linux-nvidia-bosto a version that resolves this vulnerability.Fixed in 7.0.0-2022.23 - Upgrade
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ubuntu/linux-oem-7.0to a version that resolves this vulnerability.Fixed in 7.0.0-1015.15 - Upgrade
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ubuntu/linux-oracleto a version that resolves this vulnerability.Fixed in 7.0.0-1013.13 - Upgrade
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ubuntu/linux-realtimeto a version that resolves this vulnerability.Fixed in 7.0.0-38.38.1 - Upgrade
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ubuntu/linux-riscvto a version that resolves this vulnerability.Fixed in 7.0.0-38.38.1 - Compensating control
In command_ioctl(), remove the early decrement of descriptor_busy from the loop's error path; retain the unconditional post-loop decrement so all exit paths decrement the counter exactly once.
Event History
Frequently Asked Questions
Which Ubuntu kernel package variants are listed as affected?
The listed packages are ubuntu/linux-riscv, ubuntu/linux-realtime, ubuntu/linux-hwe-edge, ubuntu/linux-azure, ubuntu/linux-gcp, ubuntu/linux-azure-fde, ubuntu/linux-gke, and ubuntu/linux-aws-5.0.
What level of access and interaction does exploitation require?
The vector indicates local access and low privileges are required. No user interaction is required.
What runtime condition leads to the use-after-free?
The condition involves an error path in gpib command_ioctl() that decrements descriptor_busy twice. A concurrent close_dev_ioctl() can then observe the counter as zero and free a descriptor that remains in use.
What security impact is indicated by the supplied severity vector?
The vector rates confidentiality, integrity, and availability impact as high. The vulnerability is classified as a use-after-free.