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MEDIUM severity

CVE-2021-36383 — xo-web

MEDIUM

CVE-2021-36383 is a medium-severity (CVSS 4.3) vulnerability in xo-web. 1 public exploit or proof-of-concept reference is indexed, so weaponization risk is real. The records list no fixed version yet; check the vendor advisory below and apply the mitigations in the meantime.

Xen Orchestra Mishandles Authorization

Published
Updated
Affected
2 pkgs
Patched
See advisory
Exploits
1 known
Exploitation data as of Nov 1, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

EPSS Exploitation Probability

via FIRST.org ↗
0.7%probability of exploitation in next 30 days
Lower Risk0.00%
Lower risk than most CVEs54th percentile — riskier than 54% of all scored CVEsHighest risk
0.00%0.40%0.81%1.21%0.1%0.7%May 26Aug 26Nov 26

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

How urgent is this, really

Where this sits among everything scored

Real-World Exposure

2 pkgs affected

How broadly this vulnerability is actually deployed: weekly install volume shows current usage, and reverse-dependency count shows how many other packages break if it stays unpatched.

0other npm packages depend on this — each one inherits the vulnerability until it's patched upstream
xo-webnpm
48downloads / week
xo-servernpm
121downloads / week

Description

Xen Orchestra (with xo-web through 5.80.0 and xo-server through 5.84.0) mishandles authorization, as demonstrated by modified WebSocket resourceSet.getAll data is which the attacker changes the permission field from none to admin. The attacker gains access to data sets such as VMs, Backups, Audit, Users, and Groups.

Affected Packages

2 total
EcosystemPackageVulnerable rangeFix
📦npmxo-weball versionsNo fix
📦npmxo-serverall versionsNo fix

Affected Products

2 products · 2 configurations
Application
xo-serverxen-orchestra
≤ 5.84.0
range
Application
xo-webxen-orchestra
≤ 5.80.0
range
Exploits & PoCs
1

Research use only. For defensive security, authorized penetration testing, and academic research only. Never execute exploit code against systems without explicit written authorization.

Xen Orchestra (with xo-web through 5.80.0 and xo-server through 5.84.0) …

github.comNVDJul 2021

Detection & mitigation playbook

Open-source dependency

  1. Detect

    Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for xo-web, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

  2. Remediation status

    The records we use list no patched version of xo-web for CVE-2021-36383. Check the maintainer's advisory, and where your build allows, override or pin the dependency away from the vulnerable range.

  3. Mitigate without a patch

    If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.

Frequently Asked Questions

Xen Orchestra (with xo-web through 5.80.0 and xo-server through 5.84.0) mishandles authorization, as demonstrated by modified WebSocket `resourceSet.getAll` data is which the attacker changes the permission field from none to admin. The attacker gains access to data sets such as VMs, Backups, Audit, Users, and Groups.
O3 Security · Impact-Aware SCA

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CVE-2021-36383: xo-web (Medium 4.3)