{"schema":"threatline.record/2","record":{"id":"CVE-2026-98745","aliases":[],"summary":"arm64/fpsimd: signal: Forbid non-streaming SVE payload on SME-only systems","details":"In the Linux kernel, the following vulnerability has been resolved:\n\narm64/fpsimd: signal: Forbid non-streaming SVE payload on SME-only systems\n\nWhen system_supports_sme() is true but system_supports_sve() is false,\nrestoring a specifically crafted SVE signal context can result in the\ntask erroneously having non-streaming SVE state. Subsequent attempts to\nmanipulate the task's FPSIMD/SVE/SME state can result in a variety of\nproblems, including fatal EL1 UNDEFs.\n\nIn such configurations, the kernel always creates an SVE signal context\nwhen delivering a signal, and this can only be in one of two states:\n\n(1) SVE_SIG_FLAG_SM is set, and an SVE payload is present containing\n    streaming mode SVE state. The recorded VL is the task's live\n    streaming VL.\n\n(2) SVE_SIG_FLAG_SM is clear, and an SVE payload is not present. The\n    FPSIMD context contains the non-streaming mode FPSIMD state. The\n    recorded VL is 0.\n\nCurrently restore_sve_fpsimd_context() correctly rejects cases where\nSVE_SIG_FLAG_SM is set and an SVE payload is not present, but fails to\nreject cases where SVE_SIG_FLAG_SM is clear and an SVE payload is\npresent. Consequently, restore_sve_fpsimd_context() can place the task\nin a state where it has non-streaming SVE state even when this is not\nsupported by HW.\n\nFor example, this can cause a later EL1 UNDEF when the kernel attempts to\nrestore the task's ZCR_EL1 value:\n\n| # ./sme-sigcontext-to-sve\n| Internal error: Oops - Undefined instruction: 0000000002000000 [#1]  SMP\n| Modules linked in:\n| CPU: 0 UID: 0 PID: 131 Comm: sme-sigcontext- Not tainted 7.3.0-rc1 #1 PREEMPT\n| Hardware name: linux,dummy-virt (DT)\n| pstate: 61402009 (nZCv daif +PAN -UAO -TCO +DIT -SSBS BTYPE=--)\n| pc : fpsimd_restore_current_state+0x258/0x458\n| lr : exit_to_user_mode_loop+0xb8/0x188\n| sp : ffff80008056be40\n| x29: ffff80008056be40 x28: fff00000c1670000 x27: 0000000000000000\n| x26: 0000000000000000 x25: 0000000000000000 x24: 0000000000000000\n| x23: ffff80008056bec0 x22: 0000000000000008 x21: 0000000000000040\n| x20: 0000000000000081 x19: 0000000008800010 x18: 0000000000000000\n| x17: 0000fffffd412570 x16: 0000000000001000 x15: 0000fffffd4123b0\n| x14: 0000fffffd412780 x13: 0000fffffd412be8 x12: 0000000047435300\n| x11: 0000fffffd412570 x10: 0000000000000000 x9 : 0000000045585401\n| x8 : fff00000c18a6c44 x7 : 0000000000000000 x6 : 0000000000000002\n| x5 : 0000000000000002 x4 : ffff800080568000 x3 : 0000000000000001\n| x2 : 0000000008800010 x1 : fff00000c1670000 x0 : 0000000008800000\n| Call trace:\n|  fpsimd_restore_current_state+0x258/0x458 (P)\n|  exit_to_user_mode_loop+0xb8/0x188\n|  el0_svc+0x1cc/0x1d0\n|  el0t_64_sync_handler+0xa0/0xe4\n|  el0t_64_sync+0x198/0x19c\n| Code: d5384101 f9400020 53175c03 36b80de0 (d5381202)\n| ---[ end trace 0000000000000000 ]---\n| Kernel panic - not syncing: Oops - Undefined instruction: Fatal exception in interrupt\n| Kernel Offset: 0x291fb1000000 from 0xffff800080000000\n| PHYS_OFFSET: 0x40000000\n| CPU features: 0x0,00000000,0052802f,ffb88f43,3afcf73f\n| Memory Limit: none\n\nRework restore_sve_fpsimd_context() to reject cases where\nSVE_SIG_FLAG_SM is clear and an SVE payload is not present. As\nparse_user_sigframe() rejects SVE signal frames when neither SVE nor SME\nare supported, it isn't necessary for restore_sve_fpsimd_context() to\nhandle the case where neither are supported.","categories":["Operating systems"],"product":"Linux","vendor":"Linux","ecosystem":null,"affected_ranges":[{"source":"CVE List","source_url":"https://www.cve.org/CVERecord?id=CVE-2026-98745","source_modified_at":"2026-10-21T12:56:21.116Z","fetched_at":"2026-10-23T18:45:31.882637Z","product":"Linux","vendor":"Linux","versions":[{"version":"7dde62f0687c8856b6c0660066c7ee83a6a6f033","lessThan":"052acee9880114879b5c221fc8dad69b786d0938","status":"affected","versionType":"git"},{"version":"7dde62f0687c8856b6c0660066c7ee83a6a6f033","lessThan":"f2338929c7663859c0c74dd6fef2c0245066f845","status":"affected","versionType":"git"},{"version":"7dde62f0687c8856b6c0660066c7ee83a6a6f033","lessThan":"2bce6f006cfe0b60e8249fd8d51396d99355cba3","status":"affected","versionType":"git"},{"version":"7dde62f0687c8856b6c0660066c7ee83a6a6f033","lessThan":"88c1c611552b24658eb61244086691c02be2013b","status":"affected","versionType":"git"},{"version":"7dde62f0687c8856b6c0660066c7ee83a6a6f033","lessThan":"e060d9069b49fe55f38057dfe592068014652671","status":"affected","versionType":"git"},{"version":"05458ee3ff82b31a4564836a84ef20d6c233dfc7","status":"affected","versionType":"git"},{"version":"6.1.7","lessThan":"6.2","status":"affected","versionType":"semver"}],"defaultStatus":"unaffected"},{"source":"CVE List","source_url":"https://www.cve.org/CVERecord?id=CVE-2026-98745","source_modified_at":"2026-10-21T12:56:21.116Z","fetched_at":"2026-10-23T18:45:31.882637Z","product":"Linux","vendor":"Linux","versions":[{"version":"6.2","status":"affected"},{"version":"0","lessThan":"6.2","status":"unaffected","versionType":"semver"},{"version":"6.6.160","lessThanOrEqual":"6.6.*","status":"unaffected","versionType":"semver"},{"version":"6.12.113","lessThanOrEqual":"6.12.*","status":"unaffected","versionType":"semver"},{"version":"6.18.56","lessThanOrEqual":"6.18.*","status":"unaffected","versionType":"semver"},{"version":"7.2.10","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-2026-98745","source_modified_at":"2026-10-21T12:56:21.116Z","fetched_at":"2026-10-23T18:45:31.882637Z","package":{"name":"Linux","ecosystem":null},"version":"052acee9880114879b5c221fc8dad69b786d0938","basis":"first unaffected version stated in the CVE record"},{"source":"CVE List","source_url":"https://www.cve.org/CVERecord?id=CVE-2026-98745","source_modified_at":"2026-10-21T12:56:21.116Z","fetched_at":"2026-10-23T18:45:31.882637Z","package":{"name":"Linux","ecosystem":null},"version":"2bce6f006cfe0b60e8249fd8d51396d99355cba3","basis":"first unaffected version stated in the CVE record"},{"source":"CVE List","source_url":"https://www.cve.org/CVERecord?id=CVE-2026-98745","source_modified_at":"2026-10-21T12:56:21.116Z","fetched_at":"2026-10-23T18:45:31.882637Z","package":{"name":"Linux","ecosystem":null},"version":"88c1c611552b24658eb61244086691c02be2013b","basis":"first unaffected version stated in the CVE record"},{"source":"CVE List","source_url":"https://www.cve.org/CVERecord?id=CVE-2026-98745","source_modified_at":"2026-10-21T12:56:21.116Z","fetched_at":"2026-10-23T18:45:31.882637Z","package":{"name":"Linux","ecosystem":null},"version":"6.2","basis":"first unaffected version stated in the CVE record"}],"cvss":null,"severity":null,"kev":{"listed":false},"epss":{"probability":0.00168,"percentile":0.05735,"score_date":"2026-10-23"},"published_at":"2026-10-18T15:47:30.967Z","modified_at":"2026-10-21T12:56:21.116Z","provenance":[{"source":"CVE List","url":"https://www.cve.org/CVERecord?id=CVE-2026-98745","fetched_at":"2026-10-23T18:45:31.882637Z","source_modified_at":"2026-10-21T12:56:21.116Z"},{"source":"EPSS","url":"https://api.first.org/data/v1/epss?cve=CVE-2026-98745","fetched_at":"2026-10-23T18:42:43.628194Z","source_modified_at":"2026-10-23"}],"sources":["CVE List","EPSS"],"references":[{"source":"CVE List","url":"https://git.kernel.org/stable/c/052acee9880114879b5c221fc8dad69b786d0938"},{"source":"CVE List","url":"https://git.kernel.org/stable/c/f2338929c7663859c0c74dd6fef2c0245066f845"},{"source":"CVE List","url":"https://git.kernel.org/stable/c/2bce6f006cfe0b60e8249fd8d51396d99355cba3"},{"source":"CVE List","url":"https://git.kernel.org/stable/c/88c1c611552b24658eb61244086691c02be2013b"},{"source":"CVE List","url":"https://git.kernel.org/stable/c/e060d9069b49fe55f38057dfe592068014652671"}],"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":"2026-10-21T12:56:21.116Z","content_hash":"969076f9a3dfd10dc4188760428a7c2c76e49e28cea0365c0cc67d48e6d29ece"}}