CVE-2026-89981 (GCVE-0-2026-89981)

Vulnerability from cvelistv5 – Published: 2026-09-16 10:32 – Updated: 2026-10-19 08:55
VLAI
Title
arm64: Don't read GMID_EL1 when MTE is disabled
Summary
In the Linux kernel, the following vulnerability has been resolved: arm64: Don't read GMID_EL1 when MTE is disabled __cpuinfo_store_cpu() gates the GMID_EL1 read on the raw ID_AA64PFR1_EL1, so it reads the register even when the kernel has disabled MTE (CONFIG_ARM64_MTE=n or arm64.nomte). KVM sets HCR_EL2.TID5 in that case, and pKVM injects an UNDEF the host cannot handle: Internal error: Oops - Undefined instruction: 0000000002000000 [#1] SMP pc : __cpuinfo_store_cpu+0xf4/0x264 Kernel panic - not syncing: Attempted to kill the idle task! Only pKVM reaches it, and only after a CPU is offlined and brought back online: its CPU_ON relay sets the host HCR before the CPU enters EL1, while plain nVHE sets it at CPUHP_AP_KVM_ONLINE. Gate the read on the CPU's own ID_AA64PFR1_EL1 with the command-line override applied, and on CONFIG_ARM64_MTE, which no register reflects. The boot CPU stores its registers before init_cpu_features() strips an unsafe override, so clamp against the hardware value here too.
Severity
No CVSS data available.
Assigner
Linux CNA under the mitre root
CNA scorecard D 53/100 over 6639 records in the last 180 days details
References
Impacted products
Vendor Product Version CPE status
Linux Linux Affected: f35abcbb8a084db4c24b66ccc8db0405c08e2f61 , < d2d22ff377cd43f2e9660426ff22e3cd4c534637 (git)
Affected: f35abcbb8a084db4c24b66ccc8db0405c08e2f61 , < 5445d64199626974269fcdf347769ad44b0bb53b (git)
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Linux Linux Affected: 7.0
Unaffected: 0 , < 7.0 (semver)
Unaffected: 7.2.5 , ≤ 7.2.* (semver)
Unaffected: 7.3 , ≤ * (original_commit_for_fix)
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{
  "containers": {
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          "product": "Linux",
          "programFiles": [
            "arch/arm64/include/asm/cpu.h",
            "arch/arm64/include/asm/cpufeature.h",
            "arch/arm64/kernel/cpufeature.c",
            "arch/arm64/kernel/cpuinfo.c"
          ],
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          "vendor": "Linux",
          "versions": [
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            }
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      ],
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          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\narm64: Don\u0027t read GMID_EL1 when MTE is disabled\n\n__cpuinfo_store_cpu() gates the GMID_EL1 read on the raw\nID_AA64PFR1_EL1, so it reads the register even when the kernel has\ndisabled MTE (CONFIG_ARM64_MTE=n or arm64.nomte). KVM sets HCR_EL2.TID5\nin that case, and pKVM injects an UNDEF the host cannot handle:\n\n  Internal error: Oops - Undefined instruction: 0000000002000000 [#1]  SMP\n  pc : __cpuinfo_store_cpu+0xf4/0x264\n  Kernel panic - not syncing: Attempted to kill the idle task!\n\nOnly pKVM reaches it, and only after a CPU is offlined and brought back\nonline: its CPU_ON relay sets the host HCR before the CPU enters EL1,\nwhile plain nVHE sets it at CPUHP_AP_KVM_ONLINE.\n\nGate the read on the CPU\u0027s own ID_AA64PFR1_EL1 with the command-line\noverride applied, and on CONFIG_ARM64_MTE, which no register reflects.\nThe boot CPU stores its registers before init_cpu_features() strips an\nunsafe override, so clamp against the hardware value here too."
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-10-19T08:55:55.850Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/d2d22ff377cd43f2e9660426ff22e3cd4c534637"
        },
        {
          "url": "https://git.kernel.org/stable/c/5445d64199626974269fcdf347769ad44b0bb53b"
        }
      ],
      "title": "arm64: Don\u0027t read GMID_EL1 when MTE is disabled",
      "x_generator": {
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      }
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  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2026-89981",
    "datePublished": "2026-09-16T10:32:58.056Z",
    "dateReserved": "2026-09-11T19:38:34.779Z",
    "dateUpdated": "2026-10-19T08:55:55.850Z",
    "state": "PUBLISHED"
  },
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  "dataVersion": "5.2",
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      "percentile": "0.09584"
    },
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        "affected": [
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                "programFiles": [
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                ],
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                  "arch/arm64/include/asm/cpufeature.h",
                  "arch/arm64/kernel/cpufeature.c",
                  "arch/arm64/kernel/cpuinfo.c"
                ],
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                "versions": [
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            ],
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          }
        ],
        "cveTags": [],
        "descriptions": [
          {
            "lang": "en",
            "value": "In the Linux kernel, the following vulnerability has been resolved:\n\narm64: Don\u0027t read GMID_EL1 when MTE is disabled\n\n__cpuinfo_store_cpu() gates the GMID_EL1 read on the raw\nID_AA64PFR1_EL1, so it reads the register even when the kernel has\ndisabled MTE (CONFIG_ARM64_MTE=n or arm64.nomte). KVM sets HCR_EL2.TID5\nin that case, and pKVM injects an UNDEF the host cannot handle:\n\n  Internal error: Oops - Undefined instruction: 0000000002000000 [#1]  SMP\n  pc : __cpuinfo_store_cpu+0xf4/0x264\n  Kernel panic - not syncing: Attempted to kill the idle task!\n\nOnly pKVM reaches it, and only after a CPU is offlined and brought back\nonline: its CPU_ON relay sets the host HCR before the CPU enters EL1,\nwhile plain nVHE sets it at CPUHP_AP_KVM_ONLINE.\n\nGate the read on the CPU\u0027s own ID_AA64PFR1_EL1 with the command-line\noverride applied, and on CONFIG_ARM64_MTE, which no register reflects.\nThe boot CPU stores its registers before init_cpu_features() strips an\nunsafe override, so clamp against the hardware value here too."
          }
        ],
        "id": "CVE-2026-89981",
        "lastModified": "2026-10-19T09:18:45.013",
        "metrics": {},
        "published": "2026-09-16T11:17:09.037",
        "references": [
          {
            "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
            "url": "https://git.kernel.org/stable/c/5445d64199626974269fcdf347769ad44b0bb53b"
          },
          {
            "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
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          }
        ],
        "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "vulnStatus": "Received"
      }
    },
    "redhat_vex": {
      "aggregate_severity": "Moderate",
      "current_release_date": "2026-11-06T01:27:10+00:00",
      "cve": "CVE-2026-89981",
      "id": "CVE-2026-89981",
      "initial_release_date": "2026-09-16T00:00:00+00:00",
      "product_status:known_affected": "1",
      "product_status:known_not_affected": "202",
      "source": "Red Hat CSAF VEX",
      "status": "final",
      "title": "kernel: arm64: Don\u0027t read GMID_EL1 when MTE is disabled",
      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-89981.json",
      "version": "3"
    }
  }
}



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