---
title: "CVE-2025-31133: runc container escape via \"masked path\" abuse due to mount race conditions"
url: https://erroneo.us/security/cve/CVE-2025-31133/
description: "CVE-2025-31133 (opencontainers runc): runc is a CLI tool for spawning and running containers according to the OCI specification. In versions 1.2.7 and…"
type: vulnerability-record
section: "Security Digest"
date_published: 2025-11-06
date_modified: 2026-10-21
publisher: erroneo.us
author: erroneo.us Security Desk
cve: "CVE-2025-31133"
kev: false
cvss: 7.3
epss: 0.00844
license: All rights reserved. Quote with attribution and a link.
---

# CVE-2025-31133: runc container escape via "masked path" abuse due to mount race conditions

**Signal:** Normal patch cycle. No exploitation signal; fix it in your next routine update if you are affected. (Computed from CISA KEV, EPSS and CVSS; not an editorial verdict.)

## Should you act?

- No confirmed exploitation. It is not in CISA’s KEV catalog and CISA’s SSVC assessment records no known exploitation. That can change quickly after a public write-up; re-check if you are affected.
- EPSS 0.8% , percentile 58: FIRST’s model estimates a 0.8% chance of exploitation activity in the next 30 days, higher than 58% of all scored CVEs (moderate). EPSS is a probability, not a verdict.
- Needs local access needed. Lower urgency for most teams unless an attacker could already run code on the machine.
- Editorial verdict: Patch this week. runc Container Escapes: Three Mount-Race CVEs Fixed — Not remotely exploitable and not seen in attacks, but anyone who runs or builds images they do not fully trust (CI runners, multi-tenant clusters) should roll out patched runc this week.

## What it is

runc is a CLI tool for spawning and running containers according to the OCI specification. In versions 1.2.7 and below, 1.3.0-rc.1 through 1.3.1, 1.4.0-rc.1 and 1.4.0-rc.2 files, runc would not perform sufficient verification that the source of the bind-mount (i.e., the container's /dev/null) was actually a real /dev/null inode when using the container's /dev/null to mask. This exposes two methods of attack: an arbitrary mount gadget, leading to host information disclosure, host denial of service, container escape, or a bypassing of maskedPaths. This issue is fixed in versions 1.2.8, 1.3.3 and 1.4.0-rc.3.

## Affected products (CVE record)

- opencontainers runc: < 1.2.8, >= 1.3.0-rc.1, < 1.3.3, >= 1.4.0-rc.1, <= 1.4.0-rc.3

## Severity

- GitHub_M CVSS 4.0: 7.3 `CVSS:4.0/AV:L/AC:L/AT:P/PR:L/UI:A/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H`

## Exploitation

- CISA KEV: not listed (no confirmed in-the-wild exploitation known to CISA).
- CISA SSVC assessment: exploitation none , automatable no , technical impact total .
- FIRST EPSS (model of 2026-10-21): 0.84% probability of exploitation activity in the next 30 days; percentile 58.

## Sources

- [CVE.org record CVE-2025-31133](https://www.cve.org/CVERecord?id=CVE-2025-31133)
- [NVD entry CVE-2025-31133](https://nvd.nist.gov/vuln/detail/CVE-2025-31133)
- [github.com](https://github.com/opencontainers/runc/security/advisories/GHSA-9493-h29p-rfm2)
- [github.com](https://github.com/opencontainers/runc/commit/1a30a8f3d921acbbb6a4bb7e99da2c05f8d48522)
- [github.com](https://github.com/opencontainers/runc/commit/5d7b2424072449872d1cd0c937f2ca25f418eb66)
- [github.com](https://github.com/opencontainers/runc/commit/8476df83b534a2522b878c0507b3491def48db9f)
- [github.com](https://github.com/opencontainers/runc/commit/db19bbed5348847da433faa9d69e9f90192bfa64)

---
Source page: https://erroneo.us/security/cve/CVE-2025-31133/ · Security Digest: https://erroneo.us/security/ · More: https://erroneo.us/llms.txt