CVE-2021-31364

CVE-2021-31364 is a medium-severity vulnerability in Juniper Junos with a CVSS 3.x base score of 5.9. 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-362.

Key facts

Description

An Improper Check for Unusual or Exceptional Conditions vulnerability combined with a Race Condition in the flow daemon (flowd) of Juniper Networks Junos OS on SRX300 Series, SRX500 Series, SRX1500, and SRX5000 Series with SPC2 allows an unauthenticated network based attacker sending specific traffic to cause a crash of the flowd/srxpfe process, responsible for traffic forwarding in SRX, which will cause a Denial of Service (DoS). Continued receipt and processing of this specific traffic will create a sustained Denial of Service (DoS) condition. This issue can only occur when specific packets are trying to create the same session and logging for session-close is configured as a policy action. Affected platforms are: SRX300 Series, SRX500 Series, SRX1500, and SRX5000 Series with SPC2. Not affected platforms are: SRX4000 Series, SRX5000 Series with SPC3, and vSRX Series. This issue affects Juniper Networks Junos OS SRX300 Series, SRX500 Series, SRX1500, and SRX5000 Series with SPC2: All versions prior to 17.4R3-S5; 18.3 versions prior to 18.3R3-S5; 18.4 versions prior to 18.4R3-S9; 19.1 versions prior to 19.1R3-S6; 19.2 versions prior to 19.2R1-S7, 19.2R3-S2; 19.3 versions prior to 19.3R2-S6, 19.3R3-S2; 19.4 versions prior to 19.4R1-S4, 19.4R3-S3; 20.1 versions prior to 20.1R2-S2, 20.1R3; 20.2 versions prior to 20.2R3; 20.3 versions prior to 20.3R2-S1, 20.3R3; 20.4 versions prior to 20.4R2.

Frequently asked questions

What is CVE-2021-31364?
An Improper Check for Unusual or Exceptional Conditions vulnerability combined with a Race Condition in the flow daemon (flowd) of Juniper Networks Junos OS on SRX300 Series, SRX500 Series, SRX1500, and SRX5000 Series with SPC2 allows an unauthenticated network based attacker sending specific traffic to cause a crash of the flowd/srxpfe process, responsible for traffic forwarding in SRX, which will cause a Denial of Service (DoS). Continued receipt and processing of this specific traffic will create a sustained Denial of Service (DoS) condition. This issue can only occur when specific packets are trying to create the same session and logging for session-close is configured as a policy action. Affected platforms are: SRX300 Series, SRX500 Series, SRX1500, and SRX5000 Series with SPC2. Not affected platforms are: SRX4000 Series, SRX5000 Series with SPC3, and vSRX Series. This issue affects Juniper Networks Junos OS SRX300 Series, SRX500 Series, SRX1500, and SRX5000 Series with SPC2: All versions prior to 17.4R3-S5; 18.3 versions prior to 18.3R3-S5; 18.4 versions prior to 18.4R3-S9; 19.1 versions prior to 19.1R3-S6; 19.2 versions prior to 19.2R1-S7, 19.2R3-S2; 19.3 versions prior to 19.3R2-S6, 19.3R3-S2; 19.4 versions prior to 19.4R1-S4, 19.4R3-S3; 20.1 versions prior to 20.1R2-S2, 20.1R3; 20.2 versions prior to 20.2R3; 20.3 versions prior to 20.3R2-S1, 20.3R3; 20.4 versions prior to 20.4R2.
How severe is CVE-2021-31364?
CVE-2021-31364 has a CVSS 3.x base score of 5.9, rated medium severity. It is exploitable over network with high attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability high.
Is CVE-2021-31364 being actively exploited?
It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (46th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2021-31364?
CVE-2021-31364 primarily affects Juniper Junos. In total, 141 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2021-31364?
Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
When was CVE-2021-31364 published?
CVE-2021-31364 was published on 2021-10-19 and last updated on 2026-06-17.

References

Affected products (141)

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