container-hardening

container-hardening is a skill for Claude Code from RedHatProductSecurity/prodsec-skills. It costs 36 tokens per session (2,388 once invoked), scanned A, original, Apache-2.0.

Guidance for securing container images and runtime settings in Dockerfiles, Containerfiles, Compose files, and Kubernetes pods.

In plain words
What is it for?
Use it to choose and pin base images, remove unused packages, run containers without root, and review Kubernetes security settings.
Why use it?
It reduces unnecessary software, limits the damage from compromised containers, and helps prevent containers from gaining excessive privileges.

Skill for Claude Code

Written for Claude Code: shipped in a Claude Code plugin.

Part of the prodsec-skills-ge-core plugin — 12 skills shipped together

Good fit Use it to choose and pin base images, remove unused packages, run containers without root, and review Kubernetes security settings.

Compare 6 skills from other repositories ↓
Install with agentmods
npx agentmods add skills/redhatproductsecurity/prodsec-skills/container-hardening
Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

Any agent
npx skills add RedHatProductSecurity/prodsec-skills --skill container-hardening
Clone the repo
git clone --depth 1 https://github.com/RedHatProductSecurity/prodsec-skills

Made for: Claude Code.

Or install prodsec-skills-ge-core, the plugin that ships this one along with the rest of its 12 skills.

Wrote this? Show the measurements

A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.

agentmods badge for container-hardening

README.md
[![agentmods](https://agentmods.dev/badge/skills/redhatproductsecurity/prodsec-skills/container-hardening/github.svg)](https://agentmods.dev/skills/redhatproductsecurity/prodsec-skills/container-hardening)
Your own site
<a href="https://agentmods.dev/skills/redhatproductsecurity/prodsec-skills/container-hardening"><img src="https://agentmods.dev/badge/skills/redhatproductsecurity/prodsec-skills/container-hardening/github.svg" alt="Measured on agentmods" height="20"></a>

Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.

agentmods 80×15 button for container-hardening

Your own site · 80×15
<a href="https://agentmods.dev/skills/redhatproductsecurity/prodsec-skills/container-hardening"><img src="https://agentmods.dev/badge/skills/redhatproductsecurity/prodsec-skills/container-hardening.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 36 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 2,388 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 1 finding. A grade says what 26 rules found in the file — not that it is safe. Third-party audits
  • NVIDIA SkillSpector warn 7 Sept 2026
SkillSpector: 1 finding, up to medium

These are SkillSpector’s own severities. On a checked sample its high-severity flags on skills were ~96% false positives — a documented command, a public API, a “never do X” rule — so we show them as a caution to read, not a verdict. Why →

  • medium Privilege Escalation · line 48
    Commands invoke sudo or root privileges. Verify this elevated access is necessary and justified.
    Fix: Avoid sudo/root unless strictly required. Prefer least-privilege patterns. If elevation is needed, document the justification and scope.
How audits are shown
Origin original No closer match found in the catalogue.
Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

ModelPer sessionOnce invoked
Fable 5.1 $0.00036 $0.02388
Opus 5 $0.00018 $0.01194
Sonnet 5 $0.00007 $0.00478
Haiku 4.5 $0.00004 $0.00239

Measured 11d ago against content hash 0047245be67e, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-10, from the pricing page.

Security

Grade A, and why

container-hardening scanned grade A with 1 finding against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 11d ago.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Asks for rootlowPrivilege escalation

A mod that escalates privileges can change anything on the machine, not only the project.

Containers must not run as root. Set `runAsNonRoot: true` and provide a numeric non-root `USER` in the Containerfile.

Downgraded: this mod is about security review, or the phrase is quoted, so it is likely naming the pattern rather than instructing it.

ge-core/container-hardening/SKILL.md · 242 lines

How it starts

The opening of the file, as written. The whole thing — 242 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Container Hardening

Secure container images and runtime configuration to reduce attack surface, prevent privilege escalation, and ensure compliance with Kubernetes security best practices.

Base Image Selection

  • Use a Universal Base Image (UBI) from the official Red Hat Container Registry
  • Prefer ubi-minimal (ubi8/ubi-minimal or ubi9/ubi-minimal) to reduce attack surface
  • Use the most up-to-date image available

Required for: all profiles (mandatory)

Image Tagging Strategy

Source Strategy
Red Hat Catalog Omit floating tags to get the latest image; exception: Konflux project uses digest-based pinning with automated updates
Non-Red Hat registries Pin the version or digest to ensure you use the intended image and not a tampered one

Minimize Installed Software

Remove non-essential packages and clean up package manager caches:

RUN microdnf upgrade -y && \
    microdnf install -y <required-packages> && \
    microdnf remove -y <unnecessary-packages> && \
    microdnf clean all

Use microdnf on ubi-minimal images; dnf on full UBI images.

Runtime Security

Non-Root Execution

Containers must not run as root. Set runAsNonRoot: true and provide a numeric non-root USER in the Containerfile.

Required for: all profiles (mandatory)

USER 1000
securityContext:
  runAsNonRoot: true
  runAsUser: 1000

Either the pod-level or container-level securityContext can set these fields. Do not use UID 0 (root) or UID 1337 (reserved for Istio sidecar proxies).

Required for: Extended (mandatory), all others (optional) — UID 1337 restriction

Privilege Restrictions

Set allowPrivilegeEscalation: false to prevent privilege escalation during container execution:

Required for: all profiles (mandatory)

securityContext:
  allowPrivilegeEscalation: false

Or in a compose file:

Read the full file on GitHub · 242 lines

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

  1. 11d ago First seen · 242 lines · 36 tokens per session scan A 0047245be67e

Subscribe to this mod's changes

container-hardening is a skill published in the GitHub repository RedHatProductSecurity/prodsec-skills (52 stars, last pushed 1mo ago), licensed Apache-2.0. It adds 36 tokens to every session and 2,388 once invoked, about $0.0002 per session on Opus 5. A static security scan graded it A with 1 finding (asks for root). No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.

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