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runc can be confused to create empty files/directories on the host

Moderate severity GitHub Reviewed Published Sep 3, 2024 in opencontainers/runc • Updated Nov 18, 2024

Package

gomod github.com/opencontainers/runc (Go)

Affected versions

< 1.1.14
>= 1.2.0-rc.1, < 1.2.0-rc.3

Patched versions

1.1.14
1.2.0-rc.3

Description

Impact

runc 1.1.13 and earlier as well as 1.2.0-rc2 and earlier can be tricked into
creating empty files or directories in arbitrary locations in the host
filesystem by sharing a volume between two containers and exploiting a race
with os.MkdirAll. While this can be used to create empty files, existing
files will not be truncated.

An attacker must have the ability to start containers using some kind of custom
volume configuration. Containers using user namespaces are still affected, but
the scope of places an attacker can create inodes can be significantly reduced.
Sufficiently strict LSM policies (SELinux/Apparmor) can also in principle block
this attack -- we suspect the industry standard SELinux policy may restrict
this attack's scope but the exact scope of protection hasn't been analysed.

This is exploitable using runc directly as well as through Docker and
Kubernetes.

The CVSS score for this vulnerability is
CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:C/C:N/I:L/A:N (Low severity, 3.6).

Workarounds

Using user namespaces restricts this attack fairly significantly such that the
attacker can only create inodes in directories that the remapped root
user/group has write access to. Unless the root user is remapped to an actual
user on the host (such as with rootless containers that don't use
/etc/sub[ug]id), this in practice means that an attacker would only be able to
create inodes in world-writable directories.

A strict enough SELinux or AppArmor policy could in principle also restrict the
scope if a specific label is applied to the runc runtime, though we haven't
thoroughly tested to what extent the standard existing policies block this
attack nor what exact policies are needed to sufficiently restrict this attack.

Patches

Fixed in runc v1.1.14 and v1.2.0-rc3.

Credits

Thanks to Rodrigo Campos Catelin (@rata) and Alban Crequy (@alban) from
Microsoft for discovering and reporting this vulnerability.

References

@cyphar cyphar published to opencontainers/runc Sep 3, 2024
Published by the National Vulnerability Database Sep 3, 2024
Published to the GitHub Advisory Database Sep 3, 2024
Reviewed Sep 3, 2024
Last updated Nov 18, 2024

Severity

Moderate

CVSS overall score

This score calculates overall vulnerability severity from 0 to 10 and is based on the Common Vulnerability Scoring System (CVSS).
/ 10

CVSS v4 base metrics

Exploitability Metrics
Attack Vector Local
Attack Complexity Low
Attack Requirements None
Privileges Required None
User interaction Passive
Vulnerable System Impact Metrics
Confidentiality None
Integrity None
Availability None
Subsequent System Impact Metrics
Confidentiality None
Integrity Low
Availability None

CVSS v4 base metrics

Exploitability Metrics
Attack Vector: This metric reflects the context by which vulnerability exploitation is possible. This metric value (and consequently the resulting severity) will be larger the more remote (logically, and physically) an attacker can be in order to exploit the vulnerable system. The assumption is that the number of potential attackers for a vulnerability that could be exploited from across a network is larger than the number of potential attackers that could exploit a vulnerability requiring physical access to a device, and therefore warrants a greater severity.
Attack Complexity: This metric captures measurable actions that must be taken by the attacker to actively evade or circumvent existing built-in security-enhancing conditions in order to obtain a working exploit. These are conditions whose primary purpose is to increase security and/or increase exploit engineering complexity. A vulnerability exploitable without a target-specific variable has a lower complexity than a vulnerability that would require non-trivial customization. This metric is meant to capture security mechanisms utilized by the vulnerable system.
Attack Requirements: This metric captures the prerequisite deployment and execution conditions or variables of the vulnerable system that enable the attack. These differ from security-enhancing techniques/technologies (ref Attack Complexity) as the primary purpose of these conditions is not to explicitly mitigate attacks, but rather, emerge naturally as a consequence of the deployment and execution of the vulnerable system.
Privileges Required: This metric describes the level of privileges an attacker must possess prior to successfully exploiting the vulnerability. The method by which the attacker obtains privileged credentials prior to the attack (e.g., free trial accounts), is outside the scope of this metric. Generally, self-service provisioned accounts do not constitute a privilege requirement if the attacker can grant themselves privileges as part of the attack.
User interaction: This metric captures the requirement for a human user, other than the attacker, to participate in the successful compromise of the vulnerable system. This metric determines whether the vulnerability can be exploited solely at the will of the attacker, or whether a separate user (or user-initiated process) must participate in some manner.
Vulnerable System Impact Metrics
Confidentiality: This metric measures the impact to the confidentiality of the information managed by the VULNERABLE SYSTEM due to a successfully exploited vulnerability. Confidentiality refers to limiting information access and disclosure to only authorized users, as well as preventing access by, or disclosure to, unauthorized ones.
Integrity: This metric measures the impact to integrity of a successfully exploited vulnerability. Integrity refers to the trustworthiness and veracity of information. Integrity of the VULNERABLE SYSTEM is impacted when an attacker makes unauthorized modification of system data. Integrity is also impacted when a system user can repudiate critical actions taken in the context of the system (e.g. due to insufficient logging).
Availability: This metric measures the impact to the availability of the VULNERABLE SYSTEM resulting from a successfully exploited vulnerability. While the Confidentiality and Integrity impact metrics apply to the loss of confidentiality or integrity of data (e.g., information, files) used by the system, this metric refers to the loss of availability of the impacted system itself, such as a networked service (e.g., web, database, email). Since availability refers to the accessibility of information resources, attacks that consume network bandwidth, processor cycles, or disk space all impact the availability of a system.
Subsequent System Impact Metrics
Confidentiality: This metric measures the impact to the confidentiality of the information managed by the SUBSEQUENT SYSTEM due to a successfully exploited vulnerability. Confidentiality refers to limiting information access and disclosure to only authorized users, as well as preventing access by, or disclosure to, unauthorized ones.
Integrity: This metric measures the impact to integrity of a successfully exploited vulnerability. Integrity refers to the trustworthiness and veracity of information. Integrity of the SUBSEQUENT SYSTEM is impacted when an attacker makes unauthorized modification of system data. Integrity is also impacted when a system user can repudiate critical actions taken in the context of the system (e.g. due to insufficient logging).
Availability: This metric measures the impact to the availability of the SUBSEQUENT SYSTEM resulting from a successfully exploited vulnerability. While the Confidentiality and Integrity impact metrics apply to the loss of confidentiality or integrity of data (e.g., information, files) used by the system, this metric refers to the loss of availability of the impacted system itself, such as a networked service (e.g., web, database, email). Since availability refers to the accessibility of information resources, attacks that consume network bandwidth, processor cycles, or disk space all impact the availability of a system.
CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:P/VC:N/VI:N/VA:N/SC:N/SI:L/SA:N/U:Green

EPSS score

0.045%
(17th percentile)

Weaknesses

CVE ID

CVE-2024-45310

GHSA ID

GHSA-jfvp-7x6p-h2pv

Source code

Credits

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