{"id":"CVE-2026-99016","revision":"173f34f3c06c47ea82e26f6ff719443c","records":[{"revision":"173f34f3c06c47ea82e26f6ff719443c","observedAt":"2026-10-23T16:01:20.601+00:00","statement":{"source":"cve-program","id":"CVE-2026-99016","aliases":[],"title":"riscv: futex: untag the user pointer before the atomic access","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nriscv: futex: untag the user pointer before the atomic access\n\naccess_ok() checks untagged_addr(uaddr), but arch_futex_atomic_op_inuser()\nand futex_atomic_cmpxchg_inatomic() hand the raw uaddr to the inline asm\namoswap/amoadd/.../lr.w+sc.w through the \"+m\" (*uaddr) operand.  When the\ntagged address ABI is enabled (CONFIG_RISCV_ISA_SUPM, prctl\nPR_SET_TAGGED_ADDR_CTRL with PMLEN != 0), those two addresses differ: a\nuser pointer whose top PMLEN bits hold a tag passes access_ok() after\nuntagging, but the atomic is then performed on the still-tagged raw\naddress.\n\nSupervisor-mode data accesses are not subject to the U-mode pointer\nmasking (that is governed by menvcfg.PMM, which the kernel does not set),\nso hardware does not strip the tag for the kernel's own access.  With\nSv57 and PMLEN=16 the tag bits overlap the canonical-address bits, so a\ntagged pointer can name a canonical kernel virtual address (e.g. in the\nlinear map) whose untagged form is a valid user address.  An unprivileged\nprocess can thus make FUTEX_WAKE_OP perform an atomic read-modify-write on\nan arbitrary kernel address, with the matching FUTEX_OP_CMP_* result\nserving as a read oracle.\n\nget_user()/put_user()/raw_copy_{to,from}_user() already untag the pointer\nafter the access_ok() check; do the same in the futex helpers so the\natomic operates on the address that was actually validated.","state":0,"publishedAt":"2026-10-23T12:20:47.859+00:00","modifiedAt":"2026-10-23T12:20:47.859+00:00","affected":[{"ecosystem":"Vendor product","name":"Linux","ranges":[],"versions":[],"rawVersionEvidence":"{\n                    \"product\": \"Linux\",\n                    \"vendor\": \"Linux\",\n                    \"defaultStatus\": \"unaffected\",\n                    \"repo\": \"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git\",\n                    \"programFiles\": [\n                        \"arch/riscv/include/asm/futex.h\"\n                    ],\n                    \"versions\": [\n                        {\n                            \"version\": \"2e1743085887ba3f553c2bb472a75a3ff744b242\",\n                            \"lessThan\": \"2e5c80bbc062a8dda33e687ebf7be8f074ee4f7d\",\n                            \"status\": \"affected\",\n                            \"versionType\": \"git\"\n                        },\n                        {\n                            \"version\": \"2e1743085887ba3f553c2bb472a75a3ff744b242\",\n                            \"lessThan\": \"8e48d8d51ab37b7decfbff3e2844e027a52ad6ea\",\n                            \"status\": \"affected\",\n                            \"versionType\": \"git\"\n                        },\n                        {\n                            \"version\": \"2e1743085887ba3f553c2bb472a75a3ff744b242\",\n                            \"lessThan\": \"405290be962b32eec842776fbe3bdf81f15b1676\",\n                            \"status\": \"affected\",\n                            \"versionType\": \"git\"\n                        }\n                    ]\n                }"},{"ecosystem":"Vendor product","name":"Linux","ranges":[],"versions":[],"rawVersionEvidence":"{\n                    \"product\": \"Linux\",\n                    \"vendor\": \"Linux\",\n                    \"defaultStatus\": \"affected\",\n                    \"repo\": \"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git\",\n                    \"programFiles\": [\n                        \"arch/riscv/include/asm/futex.h\"\n                    ],\n                    \"versions\": [\n                        {\n                            \"version\": \"6.13\",\n                            \"status\": \"affected\"\n                        },\n                        {\n                            \"version\": \"0\",\n                            \"lessThan\": \"6.13\",\n                            \"status\": \"unaffected\",\n                            \"versionType\": \"semver\"\n                        },\n                        {\n                            \"version\": \"6.18.57\",\n                            \"lessThanOrEqual\": \"6.18.*\",\n                            \"status\": \"unaffected\",\n                            \"versionType\": \"semver\"\n                        },\n                        {\n                            \"version\": \"7.2.11\",\n                            \"lessThanOrEqual\": \"7.2.*\",\n                            \"status\": \"unaffected\",\n                            \"versionType\": \"semver\"\n                        },\n                        {\n                            \"version\": \"7.3\",\n                            \"lessThanOrEqual\": \"*\",\n                            \"status\": \"unaffected\",\n                            \"versionType\": \"original_commit_for_fix\"\n                        }\n                    ]\n                }"}],"metrics":[],"references":["https://git.kernel.org/stable/c/2e5c80bbc062a8dda33e687ebf7be8f074ee4f7d","https://git.kernel.org/stable/c/8e48d8d51ab37b7decfbff3e2844e027a52ad6ea","https://git.kernel.org/stable/c/405290be962b32eec842776fbe3bdf81f15b1676"],"sourceUrl":"https://www.cve.org/CVERecord?id=CVE-2026-99016","license":"CVE Program Terms of Use","key":"cve-program:CVE-2026-99016","identifiers":["CVE-2026-99016"]},"retained":false,"historicalAffected":[]}],"coverage":[]}