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CVE-2021-43784


runc is a CLI tool for spawning and running containers on Linux according to the OCI specification. In runc, netlink is used internally as a serialization system for specifying the relevant container configuration to the `C` portion of the code (responsible for the based namespace setup of containers). In all versions of runc prior to 1.0.3, the encoder did not handle the possibility of an integer overflow in the 16-bit length field for the byte array attribute type, meaning that a large enough malicious byte array attribute could result in the length overflowing and the attribute contents being parsed as netlink messages for container configuration. This vulnerability requires the attacker to have some control over the configuration of the container and would allow the attacker to bypass the namespace restrictions of the container by simply adding their own netlink payload which disables all namespaces. The main users impacted are those who allow untrusted images with untrusted configurations to run on their machines (such as with shared cloud infrastructure). runc version 1.0.3 contains a fix for this bug. As a workaround, one may try disallowing untrusted namespace paths from your container. It should be noted that untrusted namespace paths would allow the attacker to disable namespace protections entirely even in the absence of this bug.


Security Impact Summary

This vulnerability carries a MEDIUM severity rating with a CVSS v3.1 score of 6.0, indicating it can be exploited remotely over the network but requires specific conditions to be met without requiring user interaction requiring only low-level privileges . The vulnerability impacts limited data confidentiality, limited integrity, and limited availability for affected systems. Impacting 2 products from linuxfoundation, from debian organizations running these solutions should prioritize assessment and patching.

Historical Context

Reported in 2021, this vulnerability emerged during an era marked by increased sophistication in supply chain attacks, cloud infrastructure vulnerabilities, and software-as-a-service (SaaS) security challenges. Security practices during this period emphasized zero-trust architectures, container security, and API protection.


Published

2021-12-06T18:15:08.240

Last Modified

2024-11-21T06:29:46.873

Status

Modified

Source

[email protected]

Severity

CVSSv3.1: 6.0 (MEDIUM)

CVSSv2 Vector

AV:N/AC:M/Au:S/C:P/I:P/A:P

  • Access Vector: NETWORK
  • Access Complexity: MEDIUM
  • Authentication: SINGLE
  • Confidentiality Impact: PARTIAL
  • Integrity Impact: PARTIAL
  • Availability Impact: PARTIAL
Exploitability Score

6.8

Impact Score

6.4

Weaknesses
  • Type: Secondary
    CWE-190

Affected Vendors & Products
Type Vendor Product Version/Range Vulnerable?
Application linuxfoundation runc < 1.0.3 Yes
Operating System debian debian_linux 9.0 Yes

References

How SecUtils Interprets This CVE

SecUtils normalizes and enriches National Vulnerability Database (NVD) records by standardizing vendor and product identifiers, aggregating vulnerability metadata from both NVD and MITRE sources, and providing structured context for security teams. For linuxfoundation's affected products, we extract Common Platform Enumeration (CPE) data, Common Weakness Enumeration (CWE) classifications, CVSS severity metrics, and reference data to enable rapid vulnerability prioritization and asset correlation. This record contains no exploit code, proof-of-concept instructions, or attack methodologies—only defensive intelligence necessary for patch management, risk assessment, and security operations.