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CVE-2026-89923

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Last modified

CVE-2026-89923 is a vulnerability of currently unknown severity. In the Linux kernel, the following vulnerability has been resolved: KVM: s390: Free guest debug data on vcpu destroy kvm_s390_clear_bp_data() is only called from kvm_arch_vcpu_ioctl_set_guest_debug(), i.e. when user space changes or disables debugging.

Description

In the Linux kernel, the following vulnerability has been resolved: KVM: s390: Free guest debug data on vcpu destroy kvm_s390_clear_bp_data() is only called from kvm_arch_vcpu_ioctl_set_guest_debug(), i.e. when user space changes or disables debugging. A vCPU that is destroyed while hardware breakpoints are still armed - the normal case when the VMM just exits or crashes - leaks hw_bp_info, hw_wp_info and all old_data buffers, since generic KVM frees the vCPU right after kvm_arch_vcpu_destroy(). That is bounded by MAX_BP_COUNT entries, so roughly 8 KiB per vCPU, but it is unbounded over VM lifetimes. The allocations are GFP_KERNEL_ACCOUNT, so the charge also outlives the exiting process and pins dying memcgs. Fix by clearing the debug data on vCPU destruction. Calling it unconditionally is fine: struct kvm_vcpu is zero allocated, so for a vCPU that never enabled debugging the counters are 0 and the pointers NULL.

Affected Software

Source: CNA advisory (CVE.org). NVD analysis pending.

VendorProductVersions
LinuxLinux>= 27291e2165b6de70c476b7b675308113edd69a60, < 053f2068cf9b0654b651fed5ad7649d3deb982bf; >= 27291e2165b6de70c476b7b675308113edd69a60, < 6c996b12bbe4a6023076e8eee3cfaf2cc99db76c; >= 27291e2165b6de70c476b7b675308113edd69a60, < d6280fc540d8f4653c9b54a78cb747e128070f5e; >= 27291e2165b6de70c476b7b675308113edd69a60, < 544a5a665019cef394ce8bda97fa7a2cab253781; >= 27291e2165b6de70c476b7b675308113edd69a60, < 9a32c4c6a6c23b7f5bf765eb5b83ba7f64a8ec63; >= 27291e2165b6de70c476b7b675308113edd69a60, < b5acacfdb8966abff91836c1c5bd7da59d8a526e; >= 27291e2165b6de70c476b7b675308113edd69a60, < e4d8b7f176b976474e0800ba71ee2dfa3ce263c9; >= 27291e2165b6de70c476b7b675308113edd69a60, < e7f698b09d4a7c36b299acf680fc50fe868e2bcd
LinuxLinux3.16

References

Timeline

Published
Last Modified
Status
Received

Frequently Asked Questions

What is CVE-2026-89923?
In the Linux kernel, the following vulnerability has been resolved: KVM: s390: Free guest debug data on vcpu destroy kvm_s390_clear_bp_data() is only called from kvm_arch_vcpu_ioctl_set_guest_debug(), i.e. when user space changes or disables debugging. A vCPU that is destroyed while hardware breakpoints are still armed - the normal case when the VMM just exits or crashes - leaks hw_bp_info, hw_wp_info and all old_data buffers, since generic KVM frees the vCPU right after kvm_arch_vcpu_destroy(). That is bounded by MAX_BP_COUNT entries, so roughly 8 KiB per vCPU, but it is unbounded over VM lifetimes. The allocations are GFP_KERNEL_ACCOUNT, so the charge also outlives the exiting process and pins dying memcgs. Fix by clearing the debug data on vCPU destruction. Calling it unconditionally is fine: struct kvm_vcpu is zero allocated, so for a vCPU that never enabled debugging the counters are 0 and the pointers NULL.
How severe is CVE-2026-89923?
Severity scoring for CVE-2026-89923 is pending analysis.
How do I fix CVE-2026-89923?
Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

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Source: NVD / NIST