Vulnerability Database

346,508

Total vulnerabilities in the database

CVE-2021-0271 — juniper / junos

Double Free

A Double Free vulnerability in the software forwarding interface daemon (sfid) process of Juniper Networks Junos OS allows an adjacently-connected attacker to cause a Denial of Service (DoS) by sending a crafted ARP packet to the device. Continued receipt and processing of the crafted ARP packets will create a sustained Denial of Service (DoS) condition. This issue affects: Juniper Networks Junos OS on EX2200-C Series, EX3200 Series, EX3300 Series, EX4200 Series, EX4500 Series, EX4550 Series, EX6210 Series, EX8208 Series, EX8216 Series. 12.3 versions prior to 12.3R12-S17; 15.1 versions prior to 15.1R7-S8. This issue only affects the listed Marvell-chipset based EX Series devices. No other products or platforms are affected.

  • Published: Apr 22, 2021
  • Updated: Nov 16, 2025
  • CVE: CVE-2021-0271
  • Severity: Medium
  • Exploit:

CVSS v3:

  • Severity: Medium
  • Score: 6.5
  • AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

CVSS v2:

  • Severity: Low
  • Score: 3.3
  • AV:A/AC:L/Au:N/C:N/I:N/A:P

CWEs:

Software From Fixed in
juniper / junos 12.3-r11 12.3-r11.x
juniper / junos 12.3-r1 12.3-r1.x
juniper / junos 12.3-r10 12.3-r10.x
juniper / junos 12.3-r12-s10 12.3-r12-s10.x
juniper / junos 12.3-r12 12.3-r12.x
juniper / junos 12.3-r12-s8 12.3-r12-s8.x
juniper / junos 12.3 12.3.x
juniper / junos 12.3-r12-s13 12.3-r12-s13.x
juniper / junos 12.3-r12-s14 12.3-r12-s14.x
juniper / junos 12.3-r12-s1 12.3-r12-s1.x
juniper / junos 12.3-r12-s3 12.3-r12-s3.x
juniper / junos 12.3-r12-s4 12.3-r12-s4.x
juniper / junos 12.3-r12-s6 12.3-r12-s6.x
juniper / junos 12.3-r12-s11 12.3-r12-s11.x
juniper / junos 12.3-r12-s12 12.3-r12-s12.x
juniper / junos 12.3-r10-s1 12.3-r10-s1.x
juniper / junos 12.3-r10-s2 12.3-r10-s2.x
juniper / junos 12.3-r12-s15 12.3-r12-s15.x
juniper / junos 12.3-r12-s16 12.3-r12-s16.x
juniper / junos 15.1-r7 15.1-r7.x
juniper / junos 15.1-r7-s6 15.1-r7-s6.x
juniper / junos 15.1-r7-s7 15.1-r7-s7.x
juniper / junos 15.1-r7-s4 15.1-r7-s4.x
juniper / junos 15.1-r7-s5 15.1-r7-s5.x
juniper / junos 15.1-f6-s12 15.1-f6-s12.x
juniper / junos 15.1-f2 15.1-f2.x
juniper / junos 15.1-a1 15.1-a1.x
juniper / junos 15.1-f3 15.1-f3.x
juniper / junos 15.1-r2 15.1-r2.x
juniper / junos 15.1-r4-s7 15.1-r4-s7.x
juniper / junos 15.1-f6-s10 15.1-f6-s10.x
juniper / junos 15.1-r7-s2 15.1-r7-s2.x
juniper / junos 15.1-r7-s3 15.1-r7-s3.x
juniper / junos 15.1-f6-s2 15.1-f6-s2.x
juniper / junos 15.1-f6-s1 15.1-f6-s1.x
juniper / junos 15.1-f6-s5 15.1-f6-s5.x
juniper / junos 15.1-f6-s6 15.1-f6-s6.x
juniper / junos 15.1 15.1.x
juniper / junos 15.1-r4-s8 15.1-r4-s8.x
juniper / junos 15.1-r5-s5 15.1-r5-s5.x
juniper / junos 15.1-r6-s1 15.1-r6-s1.x
juniper / junos 15.1-r5 15.1-r5.x
juniper / junos 15.1-r1 15.1-r1.x
juniper / junos 15.1-f2-s1 15.1-f2-s1.x
juniper / junos 15.1-r5-s1 15.1-r5-s1.x
juniper / junos 15.1-f5 15.1-f5.x
juniper / junos 15.1-f6-s8 15.1-f6-s8.x
juniper / junos 15.1-r5-s3 15.1-r5-s3.x
juniper / junos 15.1-r5-s6 15.1-r5-s6.x
juniper / junos 15.1-r6-s2 15.1-r6-s2.x
juniper / junos 15.1-r6-s3 15.1-r6-s3.x
juniper / junos 15.1-r6-s4 15.1-r6-s4.x
juniper / junos 15.1-f6-s9 15.1-f6-s9.x
juniper / junos 15.1-r4-s9 15.1-r4-s9.x
juniper / junos 15.1-r6-s6 15.1-r6-s6.x
juniper / junos 15.1-f 15.1-f.x
juniper / junos 15.1-f6-s3 15.1-f6-s3.x
juniper / junos 15.1-r7-s1 15.1-r7-s1.x
juniper / junos 15.1-r6 15.1-r6.x
juniper / junos 15.1-f4 15.1-f4.x
juniper / junos 15.1-r4 15.1-r4.x
juniper / junos 15.1-f2-s4 15.1-f2-s4.x
juniper / junos 15.1-f5-s7 15.1-f5-s7.x
juniper / junos 15.1-f6-s7 15.1-f6-s7.x
juniper / junos 15.1-f6 15.1-f6.x
juniper / junos 15.1-f1 15.1-f1.x
juniper / junos 15.1-f6-s4 15.1-f6-s4.x
juniper / junos 15.1-f2-s3 15.1-f2-s3.x
juniper / junos 15.1-f7 15.1-f7.x
juniper / junos 15.1-r3 15.1-r3.x
juniper / junos 15.1-r 15.1-r.x
juniper / junos 15.1-f2-s2 15.1-f2-s2.x

Frequently Asked Questions

A security vulnerability is a weakness in software, hardware, or configuration that can be exploited to compromise confidentiality, integrity, or availability. Many vulnerabilities are tracked as CVEs (Common Vulnerabilities and Exposures), which provide a standardized identifier so teams can coordinate patching, mitigation, and risk assessment across tools and vendors.

CVSS (Common Vulnerability Scoring System) estimates technical severity, but it doesn't automatically equal business risk. Prioritize using context like internet exposure, affected asset criticality, known exploitation (proof-of-concept or in-the-wild), and whether compensating controls exist. A "Medium" CVSS on an exposed, production system can be more urgent than a "Critical" on an isolated, non-production host.

A vulnerability is the underlying weakness. An exploit is the method or code used to take advantage of it. A zero-day is a vulnerability that is unknown to the vendor or has no publicly available fix when attackers begin using it. In practice, risk increases sharply when exploitation becomes reliable or widespread.

Recurring findings usually come from incomplete Asset Discovery, inconsistent patch management, inherited images, and configuration drift. In modern environments, you also need to watch the software supply chain: dependencies, containers, build pipelines, and third-party services can reintroduce the same weakness even after you patch a single host. Unknown or unmanaged assets (often called Shadow IT) are a common reason the same issues resurface.

Use a simple, repeatable triage model: focus first on externally exposed assets, high-value systems (identity, VPN, email, production), vulnerabilities with known exploits, and issues that enable remote code execution or privilege escalation. Then enforce patch SLAs and track progress using consistent metrics so remediation is steady, not reactive.

SynScan combines attack surface monitoring and continuous security auditing to keep your inventory current, flag high-impact vulnerabilities early, and help you turn raw findings into a practical remediation plan.