CVE-2021-20264

Container root escalation via writable passwd file

Published Oct 6, 2021 · Updated Aug 3, 2024

Incorrect permissions in Red Hat OpenJDK 8 and 11 containers allow local users to gain root inside the container via /etc/passwd. The affected images make /etc/passwd group-writable, enabling an unprivileged container process to add or alter an account with UID 0. Exploitation requires code execution inside the container; Red Hat reports container-level root access but no demonstrated escape to the host.

CVSS severity7.8
High
EPSS probability0.27%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Incorrect permissions in Red Hat OpenJDK 8 and 11 containers allow local users to gain root inside the container via /etc/passwd. The affected images make /etc/passwd group-writable, enabling an unprivileged container process to add or alter an account with UID 0. Exploitation requires code execution inside the container; Red Hat reports container-level root access but no demonstrated escape to the host.

The record

CVE
CVE-2021-20264
Published
Oct 6, 2021
Updated
Aug 3, 2024
Vendor
Red Hat
Product
Red Hat build of OpenJDK
Classifications
CWE-266, CWE-732, T1068
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. Oct 6, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 3, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

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

  1. Affected versionversion=openjdk 1.8

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

Red Hat · Red Hat build of OpenJDKversion=openjdk 1.8

Published CVSS scores

7.8NISTCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
4.6NISTAV:L/AC:L/Au:N/C:P/I:P/A:P

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 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectorlocal
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-266Incorrect Privilege Assignment
CWE-732Incorrect Permission Assignment for Critical Resource
T1068Exploitation for Privilege Escalation

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

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Your stack

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