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A exposição de `/proc`, `/sys` e `/var` sem a devida isolação de namespace introduz riscos de segurança significativos, incluindo aumento da superfície de ataque e divulgação de informações. Esses diretórios contêm arquivos sensíveis que, se mal configurados ou acessados por um usuário não autorizado, podem levar à fuga de contêiner, modificação do host ou fornecer informações que auxiliem ataques adicionais. Por exemplo, montar incorretamente `-v /proc:/host/proc` pode contornar a proteção do AppArmor devido à sua natureza baseada em caminho, deixando `/host/proc` desprotegido.
A exposição de `/proc`, `/sys` e `/var` sem o devido isolamento de namespace introduz riscos de segurança significativos, incluindo aumento da superfície de ataque e divulgação de informações. Esses diretórios contêm arquivos sensíveis que, se mal configurados ou acessados por um usuário não autorizado, podem levar à fuga de contêiner, modificação do host ou fornecer informações que auxiliem ataques adicionais. Por exemplo, montar incorretamente `-v /proc:/host/proc` pode contornar a proteção do AppArmor devido à sua natureza baseada em caminho, deixando `/host/proc` desprotegido.
**Você pode encontrar mais detalhes sobre cada vulnerabilidade potencial em** [**https://0xn3va.gitbook.io/cheat-sheets/container/escaping/sensitive-mounts**](https://0xn3va.gitbook.io/cheat-sheets/container/escaping/sensitive-mounts)**.**
@ -294,6 +294,7 @@ Mounting certain host Unix sockets or writable pseudo-filesystems is equivalent
/run/containerd/containerd.sock # soquete CRI do containerd
/var/run/crio/crio.sock # soquete de runtime CRI-O
/run/podman/podman.sock # API do Podman (com ou sem root)
/run/buildkit/buildkitd.sock # daemon do BuildKit (com root)
/var/run/kubelet.sock # API do Kubelet em nós do Kubernetes
/run/firecracker-containerd.sock # Kata / Firecracker
```
@ -327,7 +328,7 @@ When the last process leaves the cgroup, `/tmp/pwn` runs **as root on the host**
### Mount-Related Escape CVEs (2023-2025)
* **CVE-2024-21626 runc “Leaky Vessels” file-descriptor leak**
runc ≤1.1.11 leaked an open directory file descriptor that could point to the host root. A malicious image or `docker exec` could start a container whose *working directory* is already on the host filesystem, enabling arbitrary file read/write and privilege escalation. Fixed in runc 1.1.12 (Docker ≥25.0.3, containerd ≥1.7.14).
runc ≤ 1.1.11 leaked an open directory file descriptor that could point to the host root. A malicious image or `docker exec` could start a container whose *working directory* is already on the host filesystem, enabling arbitrary file read/write and privilege escalation. Fixed in runc 1.1.12 (Docker ≥ 25.0.3, containerd ≥ 1.7.14).
```Dockerfile
FROM scratch
@ -338,11 +339,17 @@ CMD ["/bin/sh"]
* **CVE-2024-23651 / 23653 BuildKit OverlayFS copy-up TOCTOU**
A race condition in the BuildKit snapshotter let an attacker replace a file that was about to be *copy-up* into the containers rootfs with a symlink to an arbitrary path on the host, gaining write access outside the build context. Fixed in BuildKit v0.12.5 / Buildx 0.12.0. Exploitation requires an untrusted `docker build` on a vulnerable daemon.
* **CVE-2024-1753 Buildah / Podman bind-mount breakout during `build`**
Buildah ≤ 1.35.0 (and Podman ≤ 4.9.3) incorrectly resolved absolute paths passed to `--mount=type=bind` in a *Containerfile*. A crafted build stage could mount `/` from the host **read-write** inside the build container when SELinux was disabled or in permissive mode, leading to full escape at build time. Patched in Buildah 1.35.1 and the corresponding Podman 4.9.4 back-port series.
* **CVE-2024-40635 containerd UID integer overflow**
Supplying a `User` value larger than `2147483647` in an image config overflowed the 32-bit signed integer and started the process as UID 0 inside the host user namespace. Workloads expected to run as non-root could therefore obtain root privileges. Fixed in containerd 1.6.38 / 1.7.27 / 2.0.4.
### Hardening Reminders (2025)
1. Bind-mount host paths **read-only** whenever possible and add `nosuid,nodev,noexec` mount options.
2. Prefer dedicated side-car proxies or rootless clients instead of exposing the runtime socket directly.
3. Keep the container runtime up-to-date (runc ≥1.1.12, BuildKit ≥0.12.5, containerd ≥1.7.14).
3. Keep the container runtime up-to-date (runc ≥ 1.1.12, BuildKit ≥ 0.12.5, Buildah ≥ 1.35.1 / Podman ≥ 4.9.4, containerd ≥ 1.7.27).
4. In Kubernetes, use `securityContext.readOnlyRootFilesystem: true`, the *restricted* PodSecurity profile and avoid `hostPath` volumes pointing to the paths listed above.
### References
@ -352,5 +359,7 @@ A race condition in the BuildKit snapshotter let an attacker replace a file that
- [https://0xn3va.gitbook.io/cheat-sheets/container/escaping/sensitive-mounts](https://0xn3va.gitbook.io/cheat-sheets/container/escaping/sensitive-mounts)
- [Understanding and Hardening Linux Containers](https://research.nccgroup.com/wp-content/uploads/2020/07/ncc_group_understanding_hardening_linux_containers-1-1.pdf)
- [Abusing Privileged and Unprivileged Linux Containers](https://www.nccgroup.com/globalassets/our-research/us/whitepapers/2016/june/container_whitepaper.pdf)
- [Buildah CVE-2024-1753 advisory](https://github.com/containers/buildah/security/advisories/GHSA-pmf3-c36m-g5cf)
- [containerd CVE-2024-40635 advisory](https://github.com/containerd/containerd/security/advisories/GHSA-265r-hfxg-fhmg)
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