Junos OS: mosquitto Local Privilege Escalation vulnerability in SUID binaries

published 2021-04-22 5 y ago modified 2026-06-17 4 mo ago also EUVD-2021-2875

cvss: 5.5; version 3.1, CNA
cisa kev: Not listed; not in CISA's catalog
epss: 0.2%; EPSS 0.2% chance of exploitation in 30 days, percentile 11%
public exploits: 0; none known

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.

Patch / fix

fixed in 1

Juniper Networks Junos OS 17.3R3-S12, 17.4R3-S4, 18.1R3-S12, 18.3R3-S4, 19.1R3-S4, 19.3R3-S1, 19.3R3-S2, 19.4R2-S3, 20.1R2, 20.2R1-S3, 20.2R2, 20.2R3

Exploit prediction

0.21% chance of exploitation in the next 30 days, higher than 11% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by	version	score	vector
CNA	3.1	5.5	CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N
NVD	2.0	2.1	AV:L/AC:L/Au:N/C:P/I:N/A:N

Affected products

Juniper Networks Junos OS

Classification

Weakness

CWE-250 Execution with Unnecessary Privileges
CWE-269 Improper Privilege Management

References

kb.juniper.net /JSA11175
vendor-advisory

Sources

CVE List CVE-2021-0256
NVD CVE-2021-0256

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.

Summary