{"id":"CVE-2026-98745","state":"PUBLISHED","title":"arm64/fpsimd: signal: Forbid non-streaming SVE payload on SME-only systems","description":"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.","publishedAt":"2026-10-18T15:47:30.967Z","updatedAt":"2026-10-30T12:39:17.288Z","severity":null,"assigner":"Linux","products":["Linux Linux"],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"05458ee3ff82b31a4564836a84ef20d6c233dfc7","status":"affected","lessThan":"6c5b3ec340921617d965b7c87959560e886e778f","versionType":"git"},{"version":"7dde62f0687c8856b6c0660066c7ee83a6a6f033","status":"affected","lessThan":"052acee9880114879b5c221fc8dad69b786d0938","versionType":"git"},{"version":"7dde62f0687c8856b6c0660066c7ee83a6a6f033","status":"affected","lessThan":"f2338929c7663859c0c74dd6fef2c0245066f845","versionType":"git"},{"version":"7dde62f0687c8856b6c0660066c7ee83a6a6f033","status":"affected","lessThan":"2bce6f006cfe0b60e8249fd8d51396d99355cba3","versionType":"git"},{"version":"7dde62f0687c8856b6c0660066c7ee83a6a6f033","status":"affected","lessThan":"88c1c611552b24658eb61244086691c02be2013b","versionType":"git"},{"version":"7dde62f0687c8856b6c0660066c7ee83a6a6f033","status":"affected","lessThan":"e060d9069b49fe55f38057dfe592068014652671","versionType":"git"},{"version":"6.1.7","status":"affected","lessThan":"6.1.191","versionType":"semver"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["arch/arm64/kernel/signal.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"6.2","status":"affected"},{"version":"0","status":"unaffected","lessThan":"6.2","versionType":"semver"},{"version":"6.1.191","status":"unaffected","lessThanOrEqual":"6.1.*","versionType":"semver"},{"version":"6.6.160","status":"unaffected","lessThanOrEqual":"6.6.*","versionType":"semver"},{"version":"6.12.113","status":"unaffected","lessThanOrEqual":"6.12.*","versionType":"semver"},{"version":"6.18.56","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"7.2.10","status":"unaffected","lessThanOrEqual":"7.2.*","versionType":"semver"},{"version":"7.3","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["arch/arm64/kernel/signal.c"]}],"references":["https://git.kernel.org/stable/c/6c5b3ec340921617d965b7c87959560e886e778f","https://git.kernel.org/stable/c/052acee9880114879b5c221fc8dad69b786d0938","https://git.kernel.org/stable/c/f2338929c7663859c0c74dd6fef2c0245066f845","https://git.kernel.org/stable/c/2bce6f006cfe0b60e8249fd8d51396d99355cba3","https://git.kernel.org/stable/c/88c1c611552b24658eb61244086691c02be2013b","https://git.kernel.org/stable/c/e060d9069b49fe55f38057dfe592068014652671"],"weaknesses":[],"ingestedAt":"2026-10-30T12:58:04.520Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/98xxx/CVE-2026-98745.json","commit":"1f312381e38164a43607eebab851b151dd16861e","baselineCommit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-98745","state":"PUBLISHED","datePublished":"2026-10-18T15:47:30.967Z","dateUpdated":"2026-10-30T12:39:17.288Z","assignerShortName":"Linux","assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateReserved":"2026-09-25T10:25:14.367Z"},"containers":{"cna":{"title":"arm64/fpsimd: signal: Forbid non-streaming SVE payload on SME-only systems","descriptions":[{"lang":"en","value":"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."}],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"05458ee3ff82b31a4564836a84ef20d6c233dfc7","status":"affected","lessThan":"6c5b3ec340921617d965b7c87959560e886e778f","versionType":"git"},{"version":"7dde62f0687c8856b6c0660066c7ee83a6a6f033","status":"affected","lessThan":"052acee9880114879b5c221fc8dad69b786d0938","versionType":"git"},{"version":"7dde62f0687c8856b6c0660066c7ee83a6a6f033","status":"affected","lessThan":"f2338929c7663859c0c74dd6fef2c0245066f845","versionType":"git"},{"version":"7dde62f0687c8856b6c0660066c7ee83a6a6f033","status":"affected","lessThan":"2bce6f006cfe0b60e8249fd8d51396d99355cba3","versionType":"git"},{"version":"7dde62f0687c8856b6c0660066c7ee83a6a6f033","status":"affected","lessThan":"88c1c611552b24658eb61244086691c02be2013b","versionType":"git"},{"version":"7dde62f0687c8856b6c0660066c7ee83a6a6f033","status":"affected","lessThan":"e060d9069b49fe55f38057dfe592068014652671","versionType":"git"},{"version":"6.1.7","status":"affected","lessThan":"6.1.191","versionType":"semver"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["arch/arm64/kernel/signal.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"6.2","status":"affected"},{"version":"0","status":"unaffected","lessThan":"6.2","versionType":"semver"},{"version":"6.1.191","status":"unaffected","lessThanOrEqual":"6.1.*","versionType":"semver"},{"version":"6.6.160","status":"unaffected","lessThanOrEqual":"6.6.*","versionType":"semver"},{"version":"6.12.113","status":"unaffected","lessThanOrEqual":"6.12.*","versionType":"semver"},{"version":"6.18.56","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"7.2.10","status":"unaffected","lessThanOrEqual":"7.2.*","versionType":"semver"},{"version":"7.3","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["arch/arm64/kernel/signal.c"]}],"references":[{"url":"https://git.kernel.org/stable/c/6c5b3ec340921617d965b7c87959560e886e778f"},{"url":"https://git.kernel.org/stable/c/052acee9880114879b5c221fc8dad69b786d0938"},{"url":"https://git.kernel.org/stable/c/f2338929c7663859c0c74dd6fef2c0245066f845"},{"url":"https://git.kernel.org/stable/c/2bce6f006cfe0b60e8249fd8d51396d99355cba3"},{"url":"https://git.kernel.org/stable/c/88c1c611552b24658eb61244086691c02be2013b"},{"url":"https://git.kernel.org/stable/c/e060d9069b49fe55f38057dfe592068014652671"}],"providerMetadata":{"shortName":"Linux","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateUpdated":"2026-10-30T12:39:17.288Z"},"cpeApplicability":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.1.7","versionEndExcluding":"6.1.191"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.2","versionEndExcluding":"6.6.160"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.2","versionEndExcluding":"6.12.113"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.2","versionEndExcluding":"6.18.56"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.2","versionEndExcluding":"7.2.10"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.2","versionEndExcluding":"7.3"}]}]}],"x_generator":{"engine":"bippy-1.2.0"}}}}}