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        "cveId": "CVE-2021-47123",
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        "state": "PUBLISHED",
        "assignerShortName": "Linux",
        "dateReserved": "2024-03-04T18:12:48.839Z",
        "datePublished": "2024-03-15T20:14:28.888Z",
        "dateUpdated": "2026-08-05T08:46:07.846Z"
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                    "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nio_uring: fix ltout double free on completion race\n\nAlways remove linked timeout on io_link_timeout_fn() from the master\nrequest link list, otherwise we may get use-after-free when first\nio_link_timeout_fn() puts linked timeout in the fail path, and then\nwill be found and put on master's free."
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                        "baseScore": 7.8,
                        "baseSeverity": "HIGH"
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                            "value": "AV:L - The bug is reached only through the local io_uring syscall interface (io_uring_setup/io_uring_enter) by submitting linked SQEs with IORING_OP_LINK_TIMEOUT; it is not reachable from network packet paths.\nAC:L - The race is between linked-timeout hrtimer expiry and master-request completion, both of which the attacker fully controls (timeout duration plus completing the linked op via a pipe/eventfd/etc.), so the race can be driven and retried reliably.\nPR:L - io_uring_setup and IORING_OP_LINK_TIMEOUT require only an unprivileged local account; in the affected 5.11–5.12 window there was no io_uring_disabled gate and no capability check beyond optional CAP_IPC_LOCK accounting.\nUI:N - The attacker triggers the race entirely with their own syscalls and does not need any other user to act.\nS:U - Impact is memory corruption inside the host kernel (double-free of an io_kiocb), which is a same-authority privilege-escalation scenario, not a VM/IOMMU/sandbox boundary cross.\nC:H - The bug is a double-free/use-after-free of a slab-allocated io_kiocb; a UAF on that object can be turned into an arbitrary kernel read via heap reuse.\nI:H - Double-free of the linked-timeout request enables heap spraying and write primitives against the freed io_kiocb, supporting control-flow hijacking or arbitrary kernel writes.\nA:H - The same double-free/UAF path reliably produces kernel oopses/panics even without a full exploit, so availability impact is high."
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                    "url": "https://git.kernel.org/stable/c/447c19f3b5074409c794b350b10306e1da1ef4ba"
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