CVE detail

CVE-2021-0247 — CVE-2021-0247

Published 2021-04-22 · Modified 2026-06-17 · Vendor juniper · Product junos · Source nvd
MEDIUM
severity
CVSS-derived band
5.1
CVSS v3
0–10 scale
0.0056
EPSS probability
exploitation probability, 30d
43.0%
EPSS percentile
percentile vs all CVEs
NOT LISTED
CISA KEV
known exploited catalog

Description

A Race Condition (Concurrent Execution using Shared Resource with Improper Synchronization) vulnerability in the firewall process (dfwd) of Juniper Networks Junos OS allows an attacker to bypass the firewall rule sets applied to the input loopback filter on any interfaces of a device. This issue is detectable by reviewing the PFE firewall rules, as well as the firewall counters and seeing if they are incrementing or not. For example: show firewall Filter: __default_bpdu_filter__ Filter: FILTER-INET-01 Counters: Name Bytes Packets output-match-inet 0 0 <<<<<< missing firewall packet count This issue affects: Juniper Networks Junos OS 14.1X53 versions prior to 14.1X53-D53 on QFX Series; 14.1 versions 14.1R1 and later versions prior to 15.1 versions prior to 15.1R7-S6 on QFX Series, PTX Serie

Remediation

vendor remediation guidance

The following software releases have been updated to resolve this specific issue: Junos OS 14.1X53-D53, 15.1R7-S6, 15.1X53-D593, 16.1R7-S7, 16.2R2-S11, 16.2R3, 17.1R2-S11, 17.1R3-S2, 17.2R1-S9, 17.2R3-S3, 17.3R2-S5, 17.3R3-S7, 17.4R2-S9, 17.4R3, 18.1R3-S9, 18.2R2-S6, 18.2R3-S3, 18.3R1-S7, 18.3R2-S3, 18.3R3-S1, 18.4R1-S5, 18.4R2-S3, 18.4R3, 19.1R1-S4, 19.1R2-S1, 19.1R3, 19.2R1-S3, 19.2R2, 19.3R1, and all subsequent releases.

workarounds

There are no viable workarounds for this issue.

ProductVulnerable rangeFixed versionAdvisory
Juniper Networks Junos OS>=14.1R1<14.1*14.1*advisory ↗
Juniper Networks Junos OS>=14.1X53<14.1X53-D5314.1X53-D53advisory ↗
Juniper Networks Junos OS>=15.1<15.1R7-S615.1R7-S6advisory ↗
Juniper Networks Junos OS>=15.1X53<15.1X53-D59315.1X53-D593advisory ↗
Juniper Networks Junos OS>=16.1<16.1R7-S716.1R7-S7advisory ↗
Juniper Networks Junos OS>=16.2<16.2R2-S11, 16.2R316.2R2-S11, 16.2R3advisory ↗
Juniper Networks Junos OS>=17.1<17.1R2-S11, 17.1R3-S217.1R2-S11, 17.1R3-S2advisory ↗
Juniper Networks Junos OS>=17.2<17.2R1-S9, 17.2R3-S317.2R1-S9, 17.2R3-S3advisory ↗
Juniper Networks Junos OS>=17.3<17.3R2-S5, 17.3R3-S717.3R2-S5, 17.3R3-S7advisory ↗
Juniper Networks Junos OS>=17.4<17.4R2-S9, 17.4R317.4R2-S9, 17.4R3advisory ↗
Juniper Networks Junos OS>=18.1<18.1R3-S918.1R3-S9advisory ↗
Juniper Networks Junos OS>=18.2<18.2R2-S6, 18.2R3-S318.2R2-S6, 18.2R3-S3advisory ↗
Juniper Networks Junos OS>=18.3<18.3R1-S7, 18.3R2-S3, 18.3R3-S118.3R1-S7, 18.3R2-S3, 18.3R3-S1advisory ↗
Juniper Networks Junos OS>=18.4<18.4R1-S5, 18.4R2-S3, 18.4R318.4R1-S5, 18.4R2-S3, 18.4R3advisory ↗
Juniper Networks Junos OS>=19.1<19.1R1-S4, 19.1R2-S1, 19.1R319.1R1-S4, 19.1R2-S1, 19.1R3advisory ↗
Juniper Networks Junos OS>=19.2<19.2R1-S3, 19.2R219.2R1-S3, 19.2R2advisory ↗

References

cvedb.io · NVD · CISA KEV · FIRST EPSS · vendor advisories (CVE Program List v5). Informational only, no warranty — verify every remediation against the vendor advisory before acting on it. This product uses data from the NVD API but is not endorsed or certified by the NVD, CISA, FIRST.org or any vendor named. CVE® is a registered trademark of The MITRE Corporation.