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OpenjdkApplication · Oracle

CVE-2021-20264

HIGH · 7.8 CVSS v3.1 Published 2021-10-06
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
80/100
Remediation priority · High
Zero-click

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
An insecure modification flaw in the /etc/passwd file was found in the openjdk-1.8 and openjdk-11 containers. This flaw allows an attacker with access to the container to modify the /etc/passwd and escalate their privileges. The highest threat from this vulnerability is to confidentiality, integrity, as well as system availability.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · moderate confidence

Insecure file permissions on /etc/passwd in OpenJDK container images (openjdk-1.8 and openjdk-11) allow an attacker with container access to modify this file and escalate privileges by adding malicious entries or altering existing user accounts.

MitigationEnsure /etc/passwd has correct permissions (644, owned by root) in container images and is not writable by non-privileged users; update to patched container images or rebuild with proper permissions.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
OpenjdkApplication
Affected:= 1.8.0= 11

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Local
Complexity
Low
Privileges
Low
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Identify OpenJDK version in container
    Run 'java -version' or inspect /usr/lib/jvm/ to determine if running OpenJDK 1.8.0 or 11
    Affected if Running Oracle OpenJDK container images version 1.8.0 or 11 specifically
  2. Check /etc/passwd permissions
    Run 'ls -la /etc/passwd' to view permission bits
    Affected if Permission bits are NOT 644 (rw-r--r--) - file is more permissive than expected
  3. Check /etc/passwd ownership
    Run 'stat -c "%U:%G" /etc/passwd' to view owner and group
    Affected if Ownership is not root:root or owner is not root
  4. Verify /etc/passwd is not writable by others
    Run 'stat -c "%a" /etc/passwd' to get octal permissions, or test with 'test -w /etc/passwd && echo writable' as non-root user
    Affected if The file has write permission for group or other (octal > 644)

If running OpenJDK 1.8.0 or 11 container image AND /etc/passwd has permissions more open than 644 (owned by root, writable only by owner), the environment is vulnerable to privilege escalation via /etc/passwd modification.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Mitigation available No clean upgrade yet — mitigate in the meantime
Mitigation

Ensure /etc/passwd has correct permissions (644, owned by root) in container images and is not writable by non-privileged users; update to patched container images or rebuild with proper permissions.

Recommended fix Moderate confidence
  1. Ensure the container runs with a read-only root filesystem by setting readOnlyRootFilesystem: true in the container security context
  2. Configure the container to run as a non-root user by setting runAsUser to a non-zero UID and runAsNonRoot: true in the security context
  3. Ensure /etc/passwd is not mounted from the host or is mounted read-only in the container configuration
  4. If using Kubernetes, apply a PodSecurityPolicy or security context that enforces read-only filesystem and non-root user execution
  5. Verify the container cannot write to /etc/passwd by testing write access within the container
Caveat Applications requiring write access to the root filesystem will need to be refactored to use emptyDir volumes for writable storage

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in Openjdk Scoped from the published advisory
  • Consultation2.0 h
  • Implementation2.0 h
  • Testing1.0 h
  • Review / QA1.0 h
6.0 hours of engineering $1,090
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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2021-20264 in production — separate from our analysis above.

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What this is

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What belongs here
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  • Version or environment caveats, and links to real fixes
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