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MEDIUM severity

OpenStack Nova: Nova scheduler hint injection bypasses Placement resource claims and scheduling constraintsGHSA-mfg3-p6m3-gjgr

MEDIUM

GHSA-mfg3-p6m3-gjgr is a medium-severity (CVSS 5.4) CWE-669 vulnerability in nova. A fix is available for nova — see the affected versions and patch details below.

Also known asCVE-2026-46448PYSEC-2026-2686
Published
Updated
Affected
3 pkgs
Patched
2 / 3
Exploits
None indexed
Exploitation data as of Nov 9, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

Exploitation Status

Proof-of-concept exploit code exists

  • CISA’s SSVC triage found public proof-of-concept exploit code for this CVE, though no confirmed active exploitation.

Exploitation and automatability from CISA’s SSVC triage for GHSA-mfg3-p6m3-gjgr.

EPSS Exploitation Probability

via FIRST.org ↗
0.3%probability of exploitation in next 30 days
Lower Risk0.00%
Lower risk than most CVEs20th percentile — riskier than 20% of all scored CVEsHighest risk
0.00%0.32%0.64%0.96%0.3%0.3%Jul 26Oct 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

3 pkgs affected
🐍nova🐍nova🐍nova

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects PyPI packages — download data is not available via public APIs for these ecosystems.

Description

Affects

  • Nova: >=18.0.0 <31.3.1, >=32.0.0 <32.2.1, >=33.0.0 <33.0.2

Description

Erichen from the Institute of Computing Technology, Chinese Academy of Sciences reported that Nova's server create API does not strip internal scheduler hints. An authenticated user can bypass Placement resource claims and scheduling constraint enforcement, including availability zone, host aggregate, and image trait restrictions. The resulting instance has no Placement allocation, which can lead to compute node resource exhaustion and cross-tenant data persistence on NVMe devices after instance deletion. Deployments running Nova 18.0.0 or later are affected.

Patches

Credits

  • Erichen from Institute of Computing Technology, Chinese Academy of Sciences (CVE-2026-46448)

Affected Packages

3 total 2 fixed
EcosystemPackageVulnerable rangeFix
🐍PyPInova≥ 18.0.0No fix
🐍PyPInova≥ 32.0.0&&< 32.2.132.2.1pip install --upgrade 'nova==32.2.1'
🐍PyPInova≥ 33.0.0&&< 33.0.233.0.2pip install --upgrade 'nova==33.0.2'

Affected Products

1 product · 3 configurations
Application
novaopenstack
≥ 33.0.0 && < 33.0.2
range

Detection & mitigation playbook

Open-source dependency

  1. Detect

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

  2. Fix

    A fix is available for GHSA-mfg3-p6m3-gjgr; check the affected-versions list above or the advisory for the patched release of nova, then make sure no transitive dependency still pins the vulnerable range.

  3. Workarounds

    Cap what an attacker can consume: apply request size, rate and timeout limits in front of the affected component, and run it with memory and CPU limits so exhaustion degrades one worker rather than the whole service.

Fixing This On Your OS

If you run this on a Linux distribution, patch through your package manager against the distro's own security advisory below — it tracks the exact backported fix for your release, which can ship on a different timeline (and sometimes a different severity) than the upstream project.

Red HatImportant

Red Hat OpenStack Platform (RHOSP) 16.2, 17.1, and 18.0 ship affected versions of openstack-nova and are vulnerable to this flaw. The vulnerability requires authenticated access as a project member (the default 'member' role is sufficient to create servers). The Nova API is typically network-accessible within the…

Workaround published by Red Hat
There is no configuration option to restrict which scheduler hint keys users can supply. However, operators can reduce the attack surface by: 1. Restricting access to the Nova API via network segmentation (firewall rules limiting which networks can reach the Nova API endpoint). 2. Using Keystone application credentials with limited scope to restrict which users can create servers. These mitigations reduce exposure but do not fully prevent exploitation.
Source: Red Hat security advisory for GHSA-mfg3-p6m3-gjgr (CC BY 4.0)
ProductFixed inAdvisory
Red Hat OpenStack Platform 13.0 - ELSopenstack-nova-1:17.0.13-43.el7ostRHSA-2026:94039

Frequently Asked Questions

## Affects - Nova: >=18.0.0 <31.3.1, >=32.0.0 <32.2.1, >=33.0.0 <33.0.2 ## Description Erichen from the Institute of Computing Technology, Chinese Academy of Sciences reported that Nova's server create API does not strip internal scheduler hints. An authenticated user can bypass Placement resource claims and scheduling constraint enforcement, including availability zone, host aggregate, and image trait restrictions. The resulting instance has no Placement allocation, which can lead to compute node resource exhaustion and cross-tenant data persistence on NVMe devices after instance de
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