How severe is CVE-2021-0299?

CVE-2021-0299 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-2021-0299 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (58th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2021-0299?

CVE-2021-0299 primarily affects Juniper Junos. In total, 18 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.

How do I fix CVE-2021-0299?

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-2021-0299 published?

CVE-2021-0299 was published on 2021-10-19 and last updated on 2026-06-17.

CVE-2021-0299

CVE-2021-0299 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-755.

Key facts

Severity: High (CVSS 3.x base score 7.5)
CVSS v2: 7.1
EPSS exploit prediction: 1% (58th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-755
Affected product: Juniper Junos
Published: 2021-10-19
Last modified: 2026-06-17

Description

An Improper Handling of Exceptional Conditions vulnerability in the processing of a transit or directly received malformed IPv6 packet in Juniper Networks Junos OS results in a kernel crash, causing the device to restart, leading to a Denial of Service (DoS). Continued receipt and processing of this packet will create a sustained Denial of Service (DoS) condition. This issue only affects systems with IPv6 configured. Devices with only IPv4 configured are not vulnerable to this issue. This issue affects Juniper Networks Junos OS: 19.4 versions prior to 19.4R3; 20.1 versions prior to 20.1R2; 20.2 versions prior to 20.2R1-S1, 20.2R2. This issue does not affect Juniper Networks Junos OS versions prior to 19.4R1.

Frequently asked questions

What is CVE-2021-0299?: An Improper Handling of Exceptional Conditions vulnerability in the processing of a transit or directly received malformed IPv6 packet in Juniper Networks Junos OS results in a kernel crash, causing the device to restart, leading to a Denial of Service (DoS). Continued receipt and processing of this packet will create a sustained Denial of Service (DoS) condition. This issue only affects systems with IPv6 configured. Devices with only IPv4 configured are not vulnerable to this issue. This issue affects Juniper Networks Junos OS: 19.4 versions prior to 19.4R3; 20.1 versions prior to 20.1R2; 20.2 versions prior to 20.2R1-S1, 20.2R2. This issue does not affect Juniper Networks Junos OS versions prior to 19.4R1.
How severe is CVE-2021-0299?: CVE-2021-0299 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-2021-0299 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (58th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2021-0299?: CVE-2021-0299 primarily affects Juniper Junos. In total, 18 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2021-0299?: 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-2021-0299 published?: CVE-2021-0299 was published on 2021-10-19 and last updated on 2026-06-17.

References

https://kb.juniper.net/JSA11213

Affected products (18)

cpe:2.3:o:juniper:junos:19.4:-:*:*:*:*:*:*
cpe:2.3:o:juniper:junos:19.4:r1:*:*:*:*:*:*
cpe:2.3:o:juniper:junos:19.4:r1-s1:*:*:*:*:*:*
cpe:2.3:o:juniper:junos:19.4:r1-s2:*:*:*:*:*:*
cpe:2.3:o:juniper:junos:19.4:r1-s3:*:*:*:*:*:*
cpe:2.3:o:juniper:junos:19.4:r1-s4:*:*:*:*:*:*
cpe:2.3:o:juniper:junos:19.4:r2:*:*:*:*:*:*
cpe:2.3:o:juniper:junos:19.4:r2-s1:*:*:*:*:*:*
cpe:2.3:o:juniper:junos:19.4:r2-s2:*:*:*:*:*:*
cpe:2.3:o:juniper:junos:19.4:r2-s3:*:*:*:*:*:*
cpe:2.3:o:juniper:junos:19.4:r2-s4:*:*:*:*:*:*
cpe:2.3:o:juniper:junos:19.4:r2-s5:*:*:*:*:*:*
cpe:2.3:o:juniper:junos:20.1:r1:*:*:*:*:*:*
cpe:2.3:o:juniper:junos:20.1:r1-s1:*:*:*:*:*:*
cpe:2.3:o:juniper:junos:20.1:r1-s2:*:*:*:*:*:*
cpe:2.3:o:juniper:junos:20.1:r1-s3:*:*:*:*:*:*
cpe:2.3:o:juniper:junos:20.1:r1-s4:*:*:*:*:*:*
cpe:2.3:o:juniper:junos:20.2:r1:*:*:*:*:*:*

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