CVE-2021-43784Network attack vector

Container namespace bypass via netlink length overflow

Published Dec 6, 2021 · Updated Oct 15, 2024

Integer overflow in runc before 1.0.3 allows remote authenticated users to bypass container namespace restrictions via crafted configuration. Bytemsg.Serialize casts an unchecked attribute length to a 16-bit value, so oversized data wraps and is parsed as netlink control messages. Reachability requires control of container configuration; upstream found no released build practically exploitable because namespace paths were bounded.

CVSS severity6.0
Medium
EPSS probability1.67%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
Coverage for this vulnerability

See if you're affected

Explore vulnerability checks for your environment with Hinoki.

Book a demo

Summary

What happened

Integer overflow in runc before 1.0.3 allows remote authenticated users to bypass container namespace restrictions via crafted configuration. Bytemsg.Serialize casts an unchecked attribute length to a 16-bit value, so oversized data wraps and is parsed as netlink control messages. Reachability requires control of container configuration; upstream found no released build practically exploitable because namespace paths were bounded.

The record

CVE
CVE-2021-43784
Published
Dec 6, 2021
Updated
Oct 15, 2024
Vendor
Open Container Initiative
Product
runc
Classifications
CWE-190, T1611
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Dec 6, 2021CVE publishedPublication date reported by the CVE source.
  2. Oct 15, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=< 1.0.3

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

Open Container Initiative · runcversion=< 1.0.3

Published CVSS scores

6.0GitHub, Inc.CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:C/C:L/I:L/A:L
6.0NIST NVDAV:N/AC:M/Au:S/C:P/I:P/A:P
5.0NIST NVDCVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:L/I:L/A:L

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-190Integer Overflow or Wraparound
T1611Escape to Host

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

See the directory against your own environment.

Your stack

Check the software in your environment

Book a demo to see how Hinoki identifies affected software and validates exploitability in your environment.

Book a demo