CVE intelligence and bounded remediation

CVE-2021-0256 — Juniper Junos security vulnerability

Medium CVSS 5.5

A sensitive information disclosure vulnerability in the mosquitto message broker of Juniper Networks Junos OS may allow a locally authenticated user with shell access the ability to read portions of sensitive files, such as the master.passwd file. Since mosquitto is shipped with setuid permissions enabled and is owned by the root user, this vulnerability may allow a local privileged user the ability to run mosquitto with root privileges and access sensitive information stored on the local filesystem. This issue affects Juniper Networks Junos OS: 17.3 versions prior to 17.3R3-S12, 17.4 versions prior to 17.4R3-S4; 18.1 versions prior to 18.1R3-S12; 18.3 versions prior to 18.3R3-S4; 19.1 versions prior to 19.1R3-S4; 19.3 versions prior to 19.3R3-S1, 19.3R3-S2; 19.4 versions prior to 19.4R2-S3; 20.1 versions prior to 20.1R2; 20.2 versions prior to 20.2R1-S3, 20.2R2, 20.2R3.

Severity
Medium
CVSS
5.5 (3.1)
Published
2021-04-22
CISA KEV
Not currently listed
Ecosystem
operating-system
Weaknesses
CWE-250, CWE-269

Affected products

  • juniper / junos / 17.3

Showing 1 representative product identities from 183 source matches. Confirm exact affected versions with the linked vendor and NVD evidence.

Matched remediation archetype

Privilege escalation and unsafe privilege management

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Check exposure

  • Map service accounts, operating-system identities, roles, capabilities, impersonation, set-user transitions, and administrative helper paths.
  • Determine whether untrusted users or lower-privilege processes can reach the affected transition or modify inputs it trusts.
  • Review file, socket, registry, device, job, container, and cloud-role permissions used before and after privilege changes.

Remediate safely

  • Apply the supported fix and redesign privileged operations as a minimal, authenticated, allowlisted interface.
  • Drop privileges before processing untrusted input, verify the drop succeeds, and remove unnecessary roles, capabilities, and write permissions.
  • Validate ownership and permissions at time of use and add explicit lower-to-higher privilege boundary tests.

Authoritative sources

Complete CVE record and remediation plan

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