virtio-win provides Windows paravirtualized drivers for QEMU and KVM. From mm210 until mm320, the Viosock driver permits a low-privilege local process to submit an IOCTL_SELECT request with attacker-controlled VIRTIO_VSOCK_SELECT.Fdss[*].fd_count values that overflow the 32-bit sum used by VIOSockSelect for bounds checking. The wrapped sum can pass the FD_SETSIZE check even though an individual descriptor count is much larger than the expected limit. VIOSockSelectCopyFds then iterates using the unchecked count and writes beyond the allocated pPkt->Fds array in the NonPagedPool kernel heap. Successful exploitation can corrupt kernel memory and enable privilege escalation in a Windows guest running the driver. This issue is fixed in mm320.
CVE-2026-46655
HIGHPre-NVD 7.87.8—
EchelonGraph scoreMEDIUM confidence
This high-severity CVE scores 7.8 under a secondary CVSS source (NVD's own analysis pending). EPSS exploit probability: 0.1%, top 98% of all CVEs by exploit prediction. GitHub Security Advisory data not yet ingested — confidence will rise once GHSA publishes (typical lag: hours to days for open-source ecosystem CVEs; never for infrastructure-only CVEs).
Triggered by: NVD CVSS baseline
Sources: epss, secondary
7.8EG
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
- High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS PROB: 0%CVSS: 7.8Exploit: None knownExposed: 0
No vendor fix yet — apply a workaround or compensating control (WAF / firewall / segmentation) and watch for a patch.
- CVSS v3
- 7.8
- EG Score
- 7.8(medium)
- EG Risk
- 40(Track)EG Risk 40/100SSVC: Track
EG Risk is EchelonGraph's 0–100 priority score: it fuses intrinsic severity with real-world exploitation and automatability so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner. Distinct from the 0–10 EG Score (severity).
How it’s computedSeverity78% × 45%Exploitation0% × 40%Automatability30% × 15%Action: Routine — remediate on your standard cadence. - EPSS PROB
- 0%
- EPSS %ILE
- 2%
- KEV
- Not listed
Published
September 18, 2026
Last Modified
September 18, 2026
Advisory Details (4)
Auto-updated Sep 18, 2026🔬 Proof of concept available. Patch available. Sources: github, github_pr, github_commit, github_release.
github_release Patch Available
b300 <--> mm320
Patch available: virtio-win/kvm-guest-drivers-windows mm320 (pre-release)
https://github.com/virtio-win/kvm-guest-drivers-windows/releases/tag/mm320github_commit Patch Available
commit c6bef93d7909 (virtio-win/kvm-guest-drivers-windows)
Patch available: virtio-win/kvm-guest-drivers-windows mm320 (contains commit c6bef93d7909)
https://github.com/virtio-win/kvm-guest-drivers-windows/commit/c6bef93d7909584bbda4e5c87603ea175825f342github_pr Patch Available
CVE-2026-46655: viosock: Validate fd_count in VIOSockSelect against overflow and empt…
Patch available: virtio-win/kvm-guest-drivers-windows mm320 (PR #1568 merged 2026-06-01)
https://github.com/virtio-win/kvm-guest-drivers-windows/pull/1568github Patch Available🟡 PoC Available
Integer overflow causing a heap overflow in Viosock driver · Advisory · virtio-win/kvm-guest-drivers-windows · GitHub
https://github.com/virtio-win/kvm-guest-drivers-windows/security/advisories/GHSA-qrhp-4mhp-hjwhWeakness Classification(2)
MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.
Data Freshness Timeline
(refreshed 4× in last 7d / 4× in last 30d)
Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. Most recent first.
- 2026-09-19 19:18 UTCEG score recompute
- 2026-09-18 17:26 UTCEG score recompute
- 2026-09-18 16:54 UTCEG score recompute
- 2026-09-18 16:54 UTCMITRE cvelistV5first tracked
Related CVEs(same CWE)
Frequently asked(5)
What is CVE-2026-46655?
CVE-2026-46655 is a high vulnerability published on September 18, 2026. virtio-win provides Windows paravirtualized drivers for QEMU and KVM. From mm210 until mm320, the Viosock driver permits a low-privilege local process to submit an IOCTLSELECT request with attacker-controlled VIRTIOVSOCKSELECT.Fdss[*].fdcount values that overflow the 32-bit sum used by…
When was CVE-2026-46655 disclosed?
CVE-2026-46655 was first published in the National Vulnerability Database on September 18, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-46655 actively exploited?
CVE-2026-46655 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0% probability of exploitation in the next 30 days, which ranks it in the top 97.9% of all scored CVEs.
What is the CVSS score of CVE-2026-46655?
CVE-2026-46655 has a CVSS v3 base score of 7.8 (NVD).
How do I remediate CVE-2026-46655?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-46655, EchelonGraph cross-links them in the Vendor Advisories panel below — those typically contain the canonical remediation steps, fixed version numbers, and any vendor-specific mitigations.
Dependency Blast Radius
Explore the affected products and dependency analysis for CVE-2026-46655
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