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CVE-2021-0255

Junos OS: ethtraceroute Local Privilege Escalation vulnerability in SUID binaries

Medium5.5EPSS 0.21%
Published
Updated
Reserved
Assigned by
juniper

Description

A local privilege escalation vulnerability in ethtraceroute of Juniper Networks Junos OS may allow a locally authenticated user with shell access to escalate privileges and write to the local filesystem as root. ethtraceroute is shipped with setuid permissions enabled and is owned by the root user, allowing local users to run ethtraceroute with root privileges. This issue affects Juniper Networks Junos OS: 15.1X49 versions prior to 15.1X49-D240; 17.3 versions prior to 17.3R3-S11, 17.4 versions prior to 17.4R3-S4; 18.1 versions prior to 18.1R3-S12; 18.2 versions prior to 18.2R3-S7; 18.3 versions prior to 18.3R3-S4; 18.4 versions prior to 18.4R2-S7; 19.1 versions prior to 19.1R1-S6, 19.1R2-S2, 19.1R3-S4; 19.3 versions prior to 19.3R3-S2; 19.4 versions prior to 19.4R3-S1; 20.1 versions prior to 20.1R2, 20.1R3; 20.2 versions prior to 20.2R2-S1, 20.2R3; 20.3 versions prior to 20.3R1-S1.

Scores

CVSS scores of CVE-2021-0255, by who scored it
Scored byCVSSScoreVector
juniperCNA (assigner)3.1Medium5.5CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:N
NVDNVD · Modified3.1High7.8CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
EPSS (exploitation in 30 days)
0.21% · top 90% of all CVEs (7 Nov 2026)
Loading the EPSS history…

The list uses the assigner's score when there is one, then CISA's, then NVD's: Medium 5.5.

Weakness

Affected products

  • Juniper Networks · Junos OS

    • affected 15.1X49 – < 15.1X49-D240
    • affected 17.3 – < 17.3R3-S11
    • affected 17.4 – < 17.4R3-S4
    • affected 18.1 – < 18.1R3-S12
    • affected 18.2 – < 18.2R3-S7
    • affected 18.3 – < 18.3R3-S4
    • affected 18.4 – < 18.4R2-S7
    • affected 19.1 – < 19.1R1-S6, 19.1R2-S2, 19.1R3-S4
    • affected 19.3 – < 19.3R3-S2
    • affected 19.4 – < 19.4R3-S1
    • affected 20.1 – < 20.1R2, 20.1R3
    • affected 20.2 – < 20.2R2-S1, 20.2R3
    • affected 20.3 – < 20.3R1-S1

What to do

Solution: The following software releases have been updated to resolve this specific issue: Junos OS 15.1X49-D240, 17.3R3-S11, 17.4R3-S4, 18.1R3-S12, 18.2R3-S7, 18.4R2-S7, 19.1R1-S6, 19.1R2-S2, 19.1R3-S4, 19.3R3-S2, 19.4R3-S1, 20.1R2, 20.1R3, 20.2R2-S1, 20.2R3, 20.3R1-S1, 21.1R1, and all subsequent releases. As a proactive measure to tighten the security of other Ethernet OAM utilities, setuid was also removed from other binaries, including ethping, ethdm, ethslm and ethlm.

Workaround: To reduce the risk of malicious exploitation, use access lists or firewall filters to limit CLI access to the device only from trusted, administrative networks or hosts. Additionally, limit access to the Junos OS shell to only trusted system administrators.

Exploitation: Juniper SIRT is not aware of any malicious exploitation of this vulnerability.

References (1)

Sources

The same CVE in the primary databases and aggregators, to check against.

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Record last updated .