CVE-2026-68093KVM: SVM: Bump asid_generation on CPU online to avoid ASID collision after hotplug
- —Not scoredno CVSS score yet
- 0.19%Exploitation in 30 daysEPSS · top 92% of all CVEs
- NoKnown exploitednot in CISA's KEV catalog
- NonePublic exploitsnone known yet
Description
In the Linux kernel, the following vulnerability has been resolved: KVM: SVM: Bump asid_generation on CPU online to avoid ASID collision after hotplug If a vCPU stays scheduled out (or blocked) while the last pCPU it ran on goes through a hotplug cycle (online->offline->online), and the vCPU then resumes execution on the same pCPU, then it is possible for it to run with an ASID that has now been assigned to a different vCPU, resulting in stale TLB translations being used. svm_enable_virtualization_cpu() resets asid_generation to 1 and sets next_asid to max_asid + 1 on every CPU online event, including hotplug cycles. Because next_asid starts beyond the pool boundary, the first call to new_asid() after an online event always wraps the pool, incrementing asid_generation to 2 and assigning ASIDs starting from min_asid. Consider two vCPUs from different VMs, vCPU-A pinned to CPU-X holding asid_generation=2 and ASID=N from before the hotplug event: 1. CPU-X goes offline and back online: asid_generation resets to 1, next_asid = max_asid + 1. 2. One or more vCPUs migrate to CPU-X and call new_asid(), wrapping the pool and consuming ASIDs starting from min_asid. Eventually vCPU-B from a different VM is assigned asid_generation=2, ASID=N — the same ASID that vCPU-A held before the hotplug. 3. vCPU-A enters pre_svm_run() on CPU-X: current_vmcb->cpu is unchanged so the migration branch is skipped. Its saved asid_generation=2 matches sd->asid_generation=2, so the generation check silently passes and vCPU-A continues running with ASID=N — the same ASID just freshly assigned to vCPU-B. Both vCPUs from different VMs now run on CPU-X with the same ASID, causing them to share NPT TLB entries and producing stale translations. The collision manifests as a KVM internal error (Suberror: 1, emulation failure). The NPT page fault reports a faulting GPA far outside the VM's physical memory range — a sign of stale TLB translations being used. KVM falls back to instruction emulation, which fails on FPU/XSave instructions (XRSTOR, STMXCSR) that the emulator does not implement. Fix this by incrementing asid_generation instead of resetting it to 1 in svm_enable_virtualization_cpu(). On module load, asid_generation starts at 0 (memset) and the increment produces 1, identical to the old behaviour. On subsequent hotplug cycles the generation advances beyond any value a vCPU previously observed on this CPU, so the generation check in pre_svm_run() reliably forces new_asid() on every vCPU after every hotplug cycle.
Timeline
ID reserved
By Linux
- 11 days later
· 11 days later
Published
- 3 months later
· 3 months later
Record updated
Changes after publication (a new score, a public exploit, EPSS crossing 1, 10 or 50 %, leaving KEV) are kept since November 2026; earlier ones are not known.
Scores
No CVSS score yet: neither the CNA, CISA nor NVD has scored this CVE. NVD status: Received.
- EPSS (exploitation in 30 days)
- 0.19% · top 92% of all CVEs (14 Nov 2026)
- CISA SSVC
- Exploitation: none · Automatable: no · Technical impact: partial
The list uses the assigner's score when there is one, then CISA's, then NVD's: Not scored.
Affected products
- affected 774c47f1d78e373a6bd2964f4e278d1ce26c21cb – < 2028b81321dc757b6875b99c10d908e349c141e2
- affected 774c47f1d78e373a6bd2964f4e278d1ce26c21cb – < 60283726f2845bd78b95efbd0e50b93944780477
- affected 774c47f1d78e373a6bd2964f4e278d1ce26c21cb – < 7508916b4b55d6f5ecc68cd09774dabd3a6b4440
- affected 774c47f1d78e373a6bd2964f4e278d1ce26c21cb – < 0f33b1c457c2199ed130b92cc2ff363a3f7b9415
- affected 774c47f1d78e373a6bd2964f4e278d1ce26c21cb – < 6b542d116acecb83a1ca34e8eace304cff6a4ec9
- affected 774c47f1d78e373a6bd2964f4e278d1ce26c21cb – < 25f744ffa0c8e799e06250ce2e618367b166b0d4
- affected 2.6.21
- unaffected < 2.6.21
- unaffected 6.1.183 – ≤ 6.1.*
- unaffected 6.6.148 – ≤ 6.6.*
- unaffected 6.12.101 – ≤ 6.12.*
- unaffected 6.18.42 – ≤ 6.18.*
- unaffected 7.1.6 – ≤ 7.1.*
- unaffected 7.2 – ≤ *
References
References6
- https://git.kernel.org/stable/c/2028b81321dc757b6875b99c10d908e349c141e2 (opens in a new tab)
- https://git.kernel.org/stable/c/60283726f2845bd78b95efbd0e50b93944780477 (opens in a new tab)
- https://git.kernel.org/stable/c/7508916b4b55d6f5ecc68cd09774dabd3a6b4440 (opens in a new tab)
- https://git.kernel.org/stable/c/0f33b1c457c2199ed130b92cc2ff363a3f7b9415 (opens in a new tab)
- https://git.kernel.org/stable/c/6b542d116acecb83a1ca34e8eace304cff6a4ec9 (opens in a new tab)
- https://git.kernel.org/stable/c/25f744ffa0c8e799e06250ce2e618367b166b0d4 (opens in a new tab)
Sources
The same CVE in the primary databases and aggregators, to check against.
- CVE.org record (opens in a new tab)
- CVE List JSON (GitHub) (opens in a new tab)
- NVD (opens in a new tab)
- FIRST EPSS (opens in a new tab)
- EUVD EUVD-2026-55474 (opens in a new tab)
- OSV.dev (opens in a new tab)
- GitHub Advisories (opens in a new tab)
- CIRCL Vulnerability-Lookup (opens in a new tab)
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[](https://cveledger.app/cve/CVE-2026-68093)Record last updated .