{"schema":"threatline.record/2","record":{"id":"CVE-2026-99016","aliases":[],"summary":"riscv: futex: untag the user pointer before the atomic access","details":"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.","categories":["Operating systems"],"product":"Linux","vendor":"Linux","ecosystem":null,"affected_ranges":[{"source":"CVE List","source_url":"https://www.cve.org/CVERecord?id=CVE-2026-99016","source_modified_at":"2026-10-23T12:20:47.859Z","fetched_at":"2026-10-23T18:42:43.628194Z","product":"Linux","vendor":"Linux","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"}],"defaultStatus":"unaffected"},{"source":"CVE List","source_url":"https://www.cve.org/CVERecord?id=CVE-2026-99016","source_modified_at":"2026-10-23T12:20:47.859Z","fetched_at":"2026-10-23T18:42:43.628194Z","product":"Linux","vendor":"Linux","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"}],"defaultStatus":"affected"}],"fixed_versions":[{"source":"CVE List","source_url":"https://www.cve.org/CVERecord?id=CVE-2026-99016","source_modified_at":"2026-10-23T12:20:47.859Z","fetched_at":"2026-10-23T18:42:43.628194Z","package":{"name":"Linux","ecosystem":null},"version":"2e5c80bbc062a8dda33e687ebf7be8f074ee4f7d","basis":"first unaffected version stated in the CVE record"},{"source":"CVE List","source_url":"https://www.cve.org/CVERecord?id=CVE-2026-99016","source_modified_at":"2026-10-23T12:20:47.859Z","fetched_at":"2026-10-23T18:42:43.628194Z","package":{"name":"Linux","ecosystem":null},"version":"8e48d8d51ab37b7decfbff3e2844e027a52ad6ea","basis":"first unaffected version stated in the CVE record"},{"source":"CVE List","source_url":"https://www.cve.org/CVERecord?id=CVE-2026-99016","source_modified_at":"2026-10-23T12:20:47.859Z","fetched_at":"2026-10-23T18:42:43.628194Z","package":{"name":"Linux","ecosystem":null},"version":"405290be962b32eec842776fbe3bdf81f15b1676","basis":"first unaffected version stated in the CVE record"}],"cvss":null,"severity":null,"kev":{"listed":false},"epss":{"probability":null,"percentile":null,"score_date":null},"published_at":"2026-10-23T12:20:47.859Z","modified_at":"2026-10-23T12:20:47.859Z","provenance":[{"source":"CVE List","url":"https://www.cve.org/CVERecord?id=CVE-2026-99016","fetched_at":"2026-10-23T18:42:43.628194Z","source_modified_at":"2026-10-23T12:20:47.859Z"}],"sources":["CVE List"],"references":[{"source":"CVE List","url":"https://git.kernel.org/stable/c/2e5c80bbc062a8dda33e687ebf7be8f074ee4f7d"},{"source":"CVE List","url":"https://git.kernel.org/stable/c/8e48d8d51ab37b7decfbff3e2844e027a52ad6ea"},{"source":"CVE List","url":"https://git.kernel.org/stable/c/405290be962b32eec842776fbe3bdf81f15b1676"}],"locations":[],"motoko_assessment":{"status":"requires_architecture_review","automatic_remediation":false},"cve_state":"PUBLISHED","classification":{"method":"product-first software-layer rules","rules_version":"2.1","matched_on":"product","confidence":"heuristic","reviewed":false},"change_timestamp":"2026-10-23T12:20:47.859Z","content_hash":"b158614c4f59a212610f76760a3f3bbfa5e3074a090753f275705b2bf2bf3425"}}