Processor vulnerability
CVE-2023-23583
REP MOVSB encoded with a redundant REX prefix can crash or hang the processor, and in Intel's lab could escalate from CPL 3 to CPL 0.
- Name
- Redundant Prefix Issue
- Also known as
- Reptar
- Kind
- Other
- CVE published
- 2023-11-14 CVE record
- Advisories
- INTEL-SA-00950
A REX prefix that changes nothing is legal on REP MOVSB, and
compilers do not emit one. Under certain microarchitectural
conditions, executing that encoding puts some Intel processors in an
unpredictable state: the system can crash or hang, and Intel’s own
validation found a limited case of escalation from user mode to the
kernel. Exploiting it needs the ability to run arbitrary code. Intel
lists Ice Lake, Tiger Lake, Rocket Lake, Alder Lake, Raptor Lake and
Sapphire Rapids, with the microcode revision that fixes each.What the sources say of each microarchitecture. Intel’s list gives each CPUID family, model and stepping it covers, with Intel’s mitigation for it (Software, MCU for a microcode update, or Hardware).
Affected processors
8 of the 27 microarchitectures listed are affected in all or some of their models.
| Microarchitecture | Status | Detail | Source |
|---|---|---|---|
| Ice Lake (client) | Affected | 06_7EH stepping 5 (Ice Lake U - Ice Lake Y): MCU | Intel’s list |
| Tiger Lake | Affected | 06_8CH stepping 1 (Tiger Lake U): MCU 06_8CH stepping 1 (Tiger Lake U): MCU 06_8CH stepping 2 (1. Tiger Lake U Refresh - 2. Tiger Lake H35): MCU 06_8DH stepping 1 (Tiger Lake H): MCU 06_8DH stepping 1 (Tiger Lake H): MCU | Intel’s list |
| Alder Lake | Affected | 06_97H stepping 2 (Alder Lake S (Golden Cove - Gracemont)): MCU 06_97H stepping 5 (Alder Lake S (Golden Cove - Gracemont)): MCU 06_97H stepping 5 (Catlow (Golden Cove)): MCU 06_9AH stepping 3 (1. Alder Lake H (Golden Cove - Gracemont) - 2. Alder Lake P (Golden Cove - Gracemont)): MCU 06_9AH stepping 4 (Alder Lake U (Golden Cove - Gracemont)): MCU | Intel’s list |
| Rocket Lake | Affected | 06_A7H stepping 1 (Rocket Lake): MCU | Intel’s list |
| Lunar Lake | Affected | 06_BDH stepping 1 (Lunar Lake (Lion Cove - Skymont)): MCU | Intel’s list |
| Ice Lake (server) | Affected | 06_6AH stepping 6 (Ice Lake Xeon-SP): MCU 06_6CH stepping All (Ice Lake Xeon D (Idaville)): MCU | Intel’s list |
| Raptor Lake | Some models | 06_B7H stepping 1 (1. Raptor Lake S - 2. Raptor Lake HX (Raptor Cove/Gracemont)): Not Affected 06_B7H stepping 1 (Catlow (Raptor Cove)): Not Affected 06_BAH stepping 2 - 3 - 8 (1. Raptor Lake P - 2. Raptor Lake H + refresh - 3. Raptor Lake U + refresh (Raptor Cove/Gracemont)): MCU 06_BFH stepping 2 - 5 (Raptor Lake S (Raptor Cove/Gracemont)): MCU | Intel’s list |
| Sapphire Rapids | Some models | 06_8FH stepping 5 - 6 - 7 - 8 (1. Sapphire Rapids - 2. Sapphire Rapids Edge Enhanced (Golden Cove)): MCU 06_8FH stepping 5 - 6 - 8 (Sapphire Rapids (Golden Cove) - Sapphire Rapids HBM): Not Affected | Intel’s list |
| Haswell | Not affected | 06_3FH stepping 2 (Haswell Server EP/EP4S): Not Affected 06_3FH stepping 4 (Haswell Server EX): Not Affected | Intel’s list |
| Broadwell | Not affected | 06_4FH stepping 1 (1. Broadwell Server E/EP/EP4S - 2. Broadwell Server EX): Not Affected 06_56H stepping 3 (Broadwell DE V2 - V3): Not Affected 06_56H stepping 4 (Broadwell DE Y0): Not Affected 06_56H stepping 5 (Hewitt Lake (Broadwell DE)): Not Affected | Intel’s list |
| Skylake | Not affected | 06_5EH stepping 3 (1. Skylake Xeon E3 - 2. Skylake H - 3. Skylake S): Not Affected | Intel’s list |
| Kaby Lake | Not affected | 06_8EH stepping 9 (1. Amber Lake-Y - 2. Kaby Lake U - 3. Kaby Lake U23e - 4. Kaby Lake Y): Not Affected 06_8EH stepping C (1. Whiskey Lake V - 2. Comet Lake U42 - 3. Amber Lake Y): Not Affected 06_9EH stepping 9 (1. Kaby Lake S - 2. Kaby Lake Xeon E3): Not Affected | Intel’s list |
| Coffee Lake | Not affected | 06_8EH stepping A (1. Coffee Lake U43e - 2. Whiskey Lake): Not Affected 06_8EH stepping B (Whiskey Lake U): Not Affected 06_8EH stepping C (1. Whiskey Lake V - 2. Comet Lake U42 - 3. Amber Lake Y): Not Affected 06_9EH stepping A (Coffee Lake H): Not Affected 06_9EH stepping C (Coffee Lake S): Not Affected 06_9EH stepping D (1. Coffee Lake H - 2. Coffee Lake Xeon E - 3. Coffee Lake S): Not Affected | Intel’s list |
| Comet Lake | Not affected | 06_8EH stepping C (1. Whiskey Lake V - 2. Comet Lake U42 - 3. Amber Lake Y): Not Affected 06_A5H stepping 2 (Comet Lake H): Not Affected 06_A5H stepping 3 (Comet Lake-S): Not Affected 06_A5H stepping 5 (Comet Lake-S): Not Affected 06_A6H stepping 0 (Comet Lake U62): Not Affected 06_A6H stepping 1 (Comet Lake U62): Not Affected | Intel’s list |
| Meteor Lake | Not affected | 06_AAH stepping 4 (Meteor Lake U/H/PS (Redwood Cove - Crestmont)): Not Affected | Intel’s list |
| Arrow Lake | Not affected | 06_B5H stepping 0 (Arrow Lake U (Redwood Cove - Crestmont)): Not Affected 06_C5H stepping 2 (Arrow Lake H (Lion Cove - Skymont)): Not Affected 06_C6H stepping 2 (Arrow Lake H/HX/S/S Plus (Lion Cove - Skymont)): Not Affected | Intel’s list |
| Panther Lake | Not affected | 06_CCH stepping 2 - 3 (Panther Lake (Cougar Cove - Darkmont)): Not Affected | Intel’s list |
| Skylake-SP | Not affected | 06_55H stepping 3 (Skylake Server): Not Affected 06_55H stepping 4 (1. Skylake Server - 2. Skylake D/Bakerville): Not Affected | Intel’s list |
| Cooper Lake | Not affected | 06_55H stepping B (Cooper Lake): Not Affected | Intel’s list |
| Emerald Rapids | Not affected | 06_CFH stepping 2 (Emerald Rapids (Raptor Cove)): Not Affected | Intel’s list |
| Granite Rapids | Not affected | 06_ADH stepping 1 (Granite Rapids (Redwood Cove)): Not Affected 06_ADH stepping 1 (Granite Rapids (Redwood Cove)): Not Affected 06_ADH stepping 1 (Granite Rapids R1S (Redwood Cove)): Not Affected 06_AEH stepping 1 (Granite Rapids D (Redwood Cove)/Kaseyville): Not Affected | Intel’s list |
| Sierra Forest | Not affected | 06_AFH stepping 3 (Sierra Forest (Crestmont)): Not Affected | Intel’s list |
| Clearwater Forest | Not affected | 06_DDH stepping 1 (Clearwater Forest (Darkmont)): Not Affected | Intel’s list |
| Goldmont | Not affected | 06_5CH stepping A (Apollo Lake): Not Affected 06_5FH stepping All (Denverton (Goldmont)): Not Affected | Intel’s list |
| Goldmont Plus | Not affected | 06_7AH stepping 8 (Gemini Lake): Not Affected | Intel’s list |
| Tremont | Not affected | 06_86H stepping 5 (Snow Ridge BTS (Tremont)): Not Affected 06_86H stepping 7 (Parker Ridge / Snow Ridge NS/NX/BTS): Not Affected 06_96H stepping All (Elkhart Lake (Tremont)): Not Affected 06_9CH stepping All (Jasper Lake (Tremont)): Not Affected | Intel’s list |
| Gracemont | Not affected | 06_9AH stepping 4 (Arizona Beach (Gracemont)): Not Affected 06_BEH stepping 0 (Alder Lake N (Gracemont)/Twin Lake): Not Affected | Intel’s list |
Mitigations
- Microcode: Intel's microcode update, with no performance impact Intel has seen; it can be loaded at run time. Source.
- Programs: Turning off fast strings in IA32_MISC_ENABLE avoids it without the update, at a cost Intel measured at 50% or more for some workloads, so Intel does not recommend it. Instructions: WRMSR, MOVS. Source.