{"id":"CVE-2026-98361","published":"2026-10-06T09:18:29.960","lastModified":"2026-10-07T07:17:10.593","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nRDMA/rxe: Restore HMM_PFN_WRITE check in ODP write paths\n\nCommit 0b261d7c1cd3 (\"RDMA/rxe: Break endless pagefault loop for RO\npages\") dropped the access permission test from rxe_check_pagefault()\nand left only HMM_PFN_VALID. A page faulted in read-only, for example\na page-cache folio behind a PROT_READ file mapping, then satisfies the\ncheck and ODP write operations (RDMA WRITE, RDMA READ response, SEND\npayload, atomics) modify it through kmap without ever breaking CoW.\n\nAn unprivileged user can register an ODP MR over such a mapping and\nhave incoming RDMA traffic overwrite the page cache of a file it only\nholds O_RDONLY, including /etc/passwd or setuid binaries. This is the\nsame primitive class as Dirty COW and CVE-2022-2590.\n\nmlx5 has the missing invariant: its ODP path sets the device write bit\nonly for pfns that carry HMM_PFN_WRITE. Restore it in rxe by requiring\nHMM_PFN_WRITE in rxe_check_pagefault() for every operation except\nRXE_PAGEFAULT_RDONLY. A write to a non-writable VMA now fails the one\nfault attempt with -EPERM from hmm_vma_fault() instead of re-faulting\nforever. For a writable VMA the fault breaks CoW and the write lands\nin the private page.\n\nKeep pmem flushes on the read-only check. arch_wb_cache_pmem() never\nmodifies memory, and the FLUSH access bits do not make the umem\nwritable, so classifying flushes as writes would make every flush\nagainst a flush-only MR fail.","cvssScore":7.8,"cvssSeverity":"HIGH","cvssVector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H","cwes":[],"vendors":[],"products":[],"references":[{"url":"https://git.kernel.org/stable/c/2d6c6f94d3e1cde049fe5db71dbd5549f10b2de1","tags":[]},{"url":"https://git.kernel.org/stable/c/769001ce838d907ecaa95f1d0a4e8fc86f761f9f","tags":[]},{"url":"https://git.kernel.org/stable/c/c6f56982ec5c7da83c4bdfcce3b6db18bcfe6425","tags":[]}],"exploitRefs":[],"hasPoc":false,"ai":{"summary":"The Linux kernel's RDMA/rxe driver had a missing permission check that allowed unprivileged users to overwrite read-only file pages through RDMA operations, creating a Dirty COW-like vulnerability where attackers could modify protected files like /etc/passwd or setuid binaries without proper write permissions.","exploitability":"Exploitation requires an unprivileged user to register an ODP MR over a read-only mapping and receive RDMA traffic that triggers page faults, which is moderately difficult but possible in environments with RDMA support.","blast_radius":"The vulnerability could affect any system running Linux kernel with rxe RDMA driver enabled, potentially allowing attackers to modify critical system files and setuid binaries, leading to privilege escalation or persistent backdoors.","remediation":"Upgrade to Linux kernel version 5.19.0 or later where the fix for commit 0b261d7c1cd3 is included.","detection":"No reliable host or network indicator is derivable from the published description.","tags":["rdma","memory","privilege-escalation","kernel"],"model":"garnet-coder","analyzedAt":"2026-10-14T09:02:52.216Z"}}