CVE-2023-53208
Vulnerability Scoring
Status: Awaiting Analysis
Published on: 15 Sep 2025, 15:15 UTC
CVSS Release:
CVE-2023-53208: In the Linux kernel, the following vulnerability has been resolved: KVM: nSVM: Load L1's TSC multiplier based on L1 state, not L2 state When emulating nested VM-Exit, load L1's TSC multiplier if L1's desired ratio doesn't match the current ratio, not if the ratio L1 is using for L2 diverges from the default. Functionally, the end result is the same as KVM will run L2 with L1's multiplier if L2's multiplier is the default, i.e. checking that L1's multiplier is loaded is equivalent to checking if L2 has a non-default multiplier. However, the assertion that TSC scaling is exposed to L1 is flawed, as userspace can trigger the WARN at will by writing the MSR and then updating guest CPUID to hide the feature (modifying guest CPUID is allowed anytime before KVM_RUN). E.g. hacking KVM's state_test selftest to do vcpu_set_msr(vcpu, MSR_AMD64_TSC_RATIO, 0); vcpu_clear_cpuid_feature(vcpu, X86_FEATURE_TSCRATEMSR); after restoring state in a new VM+vCPU yields an endless supply of: ------------[ cut here ]------------ WARNING: CPU: 10 PID: 206939 at arch/x86/kvm/svm/nested.c:1105 nested_svm_vmexit+0x6af/0x720 [kvm_amd] Call Trace: nested_svm_exit_handled+0x102/0x1f0 [kvm_amd] svm_handle_exit+0xb9/0x180 [kvm_amd] kvm_arch_vcpu_ioctl_run+0x1eab/0x2570 [kvm] kvm_vcpu_ioctl+0x4c9/0x5b0 [kvm] ? trace_hardirqs_off+0x4d/0xa0 __se_sys_ioctl+0x7a/0xc0 __x64_sys_ioctl+0x21/0x30 do_syscall_64+0x41/0x90 entry_SYSCALL_64_after_hwframe+0x63/0xcd Unlike the nested VMRUN path, hoisting the svm->tsc_scaling_enabled check into the if-statement is wrong as KVM needs to ensure L1's multiplier is loaded in the above scenario. Alternatively, the WARN_ON() could simply be deleted, but that would make KVM's behavior even more subtle, e.g. it's not immediately obvious why it's safe to write MSR_AMD64_TSC_RATIO when checking only tsc_ratio_msr.
The exploitability of CVE-2023-53208 depends on two key factors: attack complexity (the level of effort required to execute an exploit) and privileges required (the access level an attacker needs).
No exploitability data is available for CVE-2023-53208.
A lower complexity and fewer privilege requirements make exploitation easier. Security teams should evaluate these aspects to determine the urgency of mitigation strategies, such as patch management and access control policies.
Attack Complexity (AC) measures the difficulty in executing an exploit. A high AC means that specific conditions must be met, making an attack more challenging, while a low AC means the vulnerability can be exploited with minimal effort.
Privileges Required (PR) determine the level of system access necessary for an attack. Vulnerabilities requiring no privileges are more accessible to attackers, whereas high privilege requirements limit exploitation to authorized users with elevated access.
Above is the CVSS Sub-score Breakdown for CVE-2023-53208, illustrating how Base, Impact, and Exploitability factors combine to form the overall severity rating. A higher sub-score typically indicates a more severe or easier-to-exploit vulnerability.
Below is the Impact Analysis for CVE-2023-53208, showing how Confidentiality, Integrity, and Availability might be affected if the vulnerability is exploited. Higher values usually signal greater potential damage.
Unknown
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