CVE-2021-0227

CVE-2021-0227 is a high-severity vulnerability in Juniper Junos with a CVSS 3.x base score of 7.5. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-119.

Key facts

Description

An improper restriction of operations within the bounds of a memory buffer vulnerability in Juniper Networks Junos OS J-Web on SRX Series devices allows an attacker to cause Denial of Service (DoS) by sending certain crafted HTTP packets. Continued receipt and processing of these packets will create a sustained Denial of Service (DoS) condition. When this issue occurs, web-management, NTP daemon (ntpd) and Layer 2 Control Protocol process (L2CPD) daemons might crash. This issue affects Juniper Networks Junos OS on SRX Series: 17.3 versions prior to 17.3R3-S9; 17.4 versions prior to 17.4R2-S11, 17.4R3-S2; 18.2 versions prior to 18.2R3-S5; 18.3 versions prior to 18.3R2-S4, 18.3R3-S3; 18.4 versions prior to 18.4R2-S5, 18.4R3-S4; 19.1 versions prior to 19.1R3-S2; 19.2 versions prior to 19.2R1-S5, 19.2R3; 19.3 versions prior to 19.3R3; 19.4 versions prior to 19.4R2-S1, 19.4R3; 20.1 versions prior to 20.1R1-S2, 20.1R2;

Frequently asked questions

What is CVE-2021-0227?
An improper restriction of operations within the bounds of a memory buffer vulnerability in Juniper Networks Junos OS J-Web on SRX Series devices allows an attacker to cause Denial of Service (DoS) by sending certain crafted HTTP packets. Continued receipt and processing of these packets will create a sustained Denial of Service (DoS) condition. When this issue occurs, web-management, NTP daemon (ntpd) and Layer 2 Control Protocol process (L2CPD) daemons might crash. This issue affects Juniper Networks Junos OS on SRX Series: 17.3 versions prior to 17.3R3-S9; 17.4 versions prior to 17.4R2-S11, 17.4R3-S2; 18.2 versions prior to 18.2R3-S5; 18.3 versions prior to 18.3R2-S4, 18.3R3-S3; 18.4 versions prior to 18.4R2-S5, 18.4R3-S4; 19.1 versions prior to 19.1R3-S2; 19.2 versions prior to 19.2R1-S5, 19.2R3; 19.3 versions prior to 19.3R3; 19.4 versions prior to 19.4R2-S1, 19.4R3; 20.1 versions prior to 20.1R1-S2, 20.1R2;
How severe is CVE-2021-0227?
CVE-2021-0227 has a CVSS 3.x base score of 7.5, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability high.
Is CVE-2021-0227 being actively exploited?
It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (67th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2021-0227?
CVE-2021-0227 primarily affects Juniper Junos. In total, 128 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2021-0227?
Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.
When was CVE-2021-0227 published?
CVE-2021-0227 was published on 2021-04-22 and last updated on 2026-06-17.

References

Affected products (128)

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