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PatchSiren cyber security CVE debrief

CVE-2026-51082 Proxmox CVE debrief

CVE-2026-51082 is a race condition vulnerability between the vncproxy and vncwebsocket API calls in Proxmox Virtual Environment (PVE) 9.x pve-manager 9.1.x before 9.1.9 and 8.4.x before 8.4.19; qemu-server 9.1.x before 9.1.7 and 8.4.x before 8.4.7; and pve-container 6.1.x before 6.1.3 and 5.3.x before 5.3.4. An attacker with privileges to call 'vncproxy' can hijack a VNC session established in parallel by a different user for a different VM.

Vendor
Proxmox
Product
Proxmox Virtual Environment
CVSS
HIGH 7.2
CISA KEV
Not listed in stored evidence
Original CVE published
2026-07-17
Original CVE updated
2026-07-17
Advisory published
2026-07-17
Advisory updated
2026-07-17

Who should care

Users of Proxmox Virtual Environment (PVE) 9.x, specifically those using pve-manager 9.1.x before 9.1.9 and 8.4.x before 8.4.19; qemu-server 9.1.x before 9.1.7 and 8.4.x before 8.4.7; and pve-container 6.1.x before 6.1.3 and 5.3.x before 5.3.4, should be aware of this vulnerability and take necessary actions to mitigate it.

Technical summary

A race condition exists between the vncproxy and vncwebsocket API calls in Proxmox Virtual Environment (PVE). This vulnerability allows an attacker with privileges to call 'vncproxy' to hijack a VNC session that is established in parallel by a different user for a different VM. The affected products and versions are PVE 9.x pve-manager 9.1.x before 9.1.9 and 8.4.x before 8.4.19; qemu-server 9.1.x before 9.1.7 and 8.4.x before 8.4.7; and pve-container 6.1.x before 6.1.3 and 5.3.x before 5.3.4.

Defensive priority

High

Recommended defensive actions

  • Update pve-manager to version 9.1.9 or later for PVE 9.x, and to version 8.4.19 or later for PVE 8.4.x.
  • Update qemu-server to version 9.1.7 or later for PVE 9.x, and to version 8.4.7 or later for PVE 8.4.x.
  • Update pve-container to version 6.1.3 or later for PVE 6.1.x, and to version 5.3.4 or later for PVE 5.3.x.
  • Restrict access to the vncproxy API call to only those who need it.
  • Monitor VNC sessions for suspicious activity.

Evidence notes

The CVE record was published on 2026-07-17T15:16:46.867Z and has not been modified since then. The NVD entry is currently 'Received'. Evidence is limited; defenders should verify affected product deployments exist in managed environments and review official advisories for scope, severity, and guidance. Confirm compensating controls are in place for exposed systems and monitor for suspicious VNC session activity. Check relevant logs for exposed assets needing extra review.

Sources and references

Verified primary and authoritative sources

  • CVE-2026-51082 CVE Program record

    Publisher, destination, and source semantics verified

    URL: https://www.cve.org/CVERecord?id=CVE-2026-51082

    CVE Program - Official CVE Program record with source-provided CVE metadata.

  • CVE-2026-51082 NVD vulnerability detail

    Publisher, destination, and source semantics verified

    URL: https://nvd.nist.gov/vuln/detail/CVE-2026-51082

    NIST National Vulnerability Database - Official NIST NVD detail page and source-specific vulnerability assessment.

Supplemental references

  • Source reference

    Unverified legacy reference

    URL: https://forum.proxmox.com/threads/proxmox-virtual-environment-security-advisories.149331/post-849971

    [email protected]

Methodology and review provenance

AI-assisted synthesis based on stored public vulnerability evidence. System validation, approval state, and publication status do not by themselves establish human review of this revision. PatchSiren helps prioritize defensive review and does not prove exposure or remediation on any system.