Security Digest · Vulnerability record
CVE-2025-31133: runc container escape via "masked path" abuse due to mount race conditions
runc is a CLI tool for spawning and running containers according to the OCI specification.
CVSS 7.3 High EPSS 0.8% · p58 Patch this week
Should you act?
Normal patch cycle
No exploitation signal; fix it in your next routine update if you are affected. This signal is computed from CISA KEV, EPSS and CVSS data; it is not an editorial verdict.
- 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.
Weakness type: CWE-61, CWE-363.
Product: opencontainers runc · Assigned by: GitHub_M · Published: 2025-11-06
Affected and fixed versions
| Vendor | Product | Affected versions (per 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 scores
| Scored by | CVSS | Score | Vector |
|---|---|---|---|
| GitHub_M | 4.0 | 7.3 High | 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 |
- Attack vector: local access needed
- Attack complexity: low
- Attack requirements: present (depends on deployment conditions)
- Privileges required: low (any account)
- User interaction: active
CVSS measures how bad a flaw is if exploited, not how likely exploitation is. Read it next to the exploitation data below.
Exploitation and urgency
- 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.
Timeline
- — erroneo.us brief: runc Container Escapes: Three Mount-Race CVEs Fixed
- — CVE record last updated
- — CVE record published by GitHub_M
Sources and references
Original sources first. Version and fix details should always be confirmed against the vendor or project advisory.
Vulnerability records
- CVE.org record CVE-2025-31133 cve.org
- NVD entry CVE-2025-31133 nvd.nist.gov
Other references from the CVE record and advisory
- github.com github.com
- github.com github.com
- github.com github.com
- github.com github.com
- github.com github.com