{ "dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": { "cveId": "CVE-2026-99016", "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "state": "PUBLISHED", "assignerShortName": "Linux", "dateReserved": "2026-09-25T10:25:14.386Z", "datePublished": "2026-10-23T12:20:47.859Z", "dateUpdated": "2026-10-24T14:10:03.722Z" }, "containers": { "cna": { "providerMetadata": { "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "shortName": "Linux", "dateUpdated": "2026-10-24T14:10:03.722Z" }, "descriptions": [ { "lang": "en", "value": "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." } ], "metrics": [ { "cvssV3_1": { "version": "3.1", "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H", "baseScore": 7.8, "baseSeverity": "HIGH" }, "scenarios": [ { "lang": "en", "value": "AV:L - `sys_futex(FUTEX_WAKE_OP_PRIVATE)` follows `do_futex()` → `futex_wake_op()` → `futex_atomic_op_inuser()` → the patched `arch_futex_atomic_op_inuser()` using attacker-supplied `uaddr2`; no network data reaches this local syscall path.\nAC:L - On an affected Sv57 system supporting PMLEN=16, the attacker deterministically enables tagged addresses with `prctl()` and supplies a canonical linear-map pointer; no race, victim state, or second actor is required.\nPR:L - `sys_prctl(PR_SET_TAGGED_ADDR_CTRL)` and `sys_futex()` contain no capability or credential checks, so an ordinary unprivileged process can enable PMLEN=16 and invoke `FUTEX_WAKE_OP_PRIVATE`.\nUI:N - The attacking process performs both `prctl()` setup and the futex operations itself; no victim must open, mount, approve, or otherwise act.\nS:U - The AMO instructions corrupt the host kernel's own linear-map memory, producing ordinary local kernel privilege escalation without crossing a VM, IOMMU, or separate security authority.\nC:H - The raw-address AMO returns the prior 32-bit kernel value to `futex_atomic_op_inuser()`, whose `FUTEX_OP_CMP_*` result can be observed through controlled waiters, providing a repeatable read oracle over direct-mapped physical memory.\nI:H - `arch_futex_atomic_op_inuser()` executes `amoswap`, `amoadd`, `amoor`, `amoand`, or `amoxor` at the chosen kernel address; SET followed by shifted OR operations permits controlled 32-bit kernel-memory writes and privilege escalation.\nA:H - The same chosen-address AMOs can overwrite direct-mapped kernel objects, credentials, or page-table memory; corrupting such live kernel state can reliably cause an oops, panic, or complete system failure." } ] } ], "affected": [ { "product": "Linux", "vendor": "Linux", "defaultStatus": "unaffected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": [ "arch/riscv/include/asm/futex.h" ], "versions": [ { "version": "2e1743085887ba3f553c2bb472a75a3ff744b242", "lessThan": "2e5c80bbc062a8dda33e687ebf7be8f074ee4f7d", "status": "affected", "versionType": "git" }, { "version": "2e1743085887ba3f553c2bb472a75a3ff744b242", "lessThan": "8e48d8d51ab37b7decfbff3e2844e027a52ad6ea", "status": "affected", "versionType": "git" }, { "version": "2e1743085887ba3f553c2bb472a75a3ff744b242", "lessThan": "405290be962b32eec842776fbe3bdf81f15b1676", "status": "affected", "versionType": "git" } ] }, { "product": "Linux", "vendor": "Linux", "defaultStatus": "affected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": [ "arch/riscv/include/asm/futex.h" ], "versions": [ { "version": "6.13", "status": "affected" }, { "version": "0", "lessThan": "6.13", "status": "unaffected", "versionType": "semver" }, { "version": "6.18.57", "lessThanOrEqual": "6.18.*", "status": "unaffected", "versionType": "semver" }, { "version": "7.2.11", "lessThanOrEqual": "7.2.*", "status": "unaffected", "versionType": "semver" }, { "version": "7.3", "lessThanOrEqual": "*", "status": "unaffected", "versionType": "original_commit_for_fix" } ] } ], "cpeApplicability": [ { "nodes": [ { "operator": "OR", "negate": false, "cpeMatch": [ { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.13", "versionEndExcluding": "6.18.57" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.13", "versionEndExcluding": "7.2.11" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.13", "versionEndExcluding": "7.3" } ] } ] } ], "references": [ { "url": "https://git.kernel.org/stable/c/2e5c80bbc062a8dda33e687ebf7be8f074ee4f7d" }, { "url": "https://git.kernel.org/stable/c/8e48d8d51ab37b7decfbff3e2844e027a52ad6ea" }, { "url": "https://git.kernel.org/stable/c/405290be962b32eec842776fbe3bdf81f15b1676" } ], "title": "riscv: futex: untag the user pointer before the atomic access", "x_generator": { "engine": "bippy-1.2.0" } } } }