Security readout for executives and security teams
Plain-English summary
Certain Juniper SRX firewalls can crash their traffic-forwarding process when session-close logging is configured and specific network traffic is received. An unauthenticated attacker could cause denial of service, and repeated traffic could keep the device unavailable. Exposure depends on platform, Junos OS branch, SPC generation, and a specific policy logging configuration.
Executive priority
Treat this as a moderate-priority firewall availability risk. It does not expose data or allow code execution, but it can disrupt traffic forwarding on affected SRX deployments. Prioritize remediation where SRX devices support critical network paths and the vulnerable logging condition exists.
Technical view
CVE-2021-31364 is an improper exceptional-condition check combined with a race condition in Junos OS flowd. On affected SRX300, SRX500, SRX1500, and SRX5000 with SPC2, specific traffic attempting to create the same session can crash flowd/srxpfe when session-close logging is a policy action. The impact is availability loss only.
Likely exposure
Most likely exposure is internet- or network-reachable Juniper SRX devices on affected Junos OS releases where security policies use log session-close. SRX4000, SRX5000 with SPC3, and vSRX are listed as not affected in the provided source bundle.
Exploitation context
The sources describe unauthenticated network-based denial of service with high attack complexity. CISA KEV is false in the provided bundle, and no cited source states active exploitation. Sustained denial of service requires continued receipt and processing of the specific traffic.
Researcher notes
The vulnerability is configuration-dependent and platform-specific. Validation should focus on model family, SPC generation, Junos OS branch, and policy logging state. Do not assume vSRX, SRX4000, or SRX5000 with SPC3 are affected because the provided description explicitly excludes them.
Mitigation direction
- Identify affected SRX models, Junos OS branches, and SRX5000 SPC2 deployments.
- Upgrade affected devices to the Junos OS fixed release for their branch.
- Review Juniper advisory JSA11226 before selecting the target maintenance release.
- If upgrade is delayed, review policies using log session-close with vendor guidance.
- Prioritize firewalls protecting critical traffic paths or exposed network edges.
Validation and detection
- Inventory SRX300, SRX500, SRX1500, and SRX5000 SPC2 devices.
- Compare installed Junos OS versions against the affected version ranges.
- Check security policies for session-close logging as a policy action.
- Review logs and monitoring for flowd or srxpfe crash events.
- Confirm upgraded devices report a fixed Junos OS release.
Public sources used
Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.
Conservative CVE-to-ATT&CK context
These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.
ATT&CK lookup starting points
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CWE-362: Exact CWE lookup
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Open ATT&CK lookupCWE-754: Exact CWE lookup
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Open ATT&CK lookupCVE-2021-31364 mapping review
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Open ATT&CK lookup- Severity
- Medium
- CVSS
- 5.9 (3.1)
- Known Exploited
- No
- Published
Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H
CNA and ADP enrichment extracted from CVE v5
These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.
CVSS vector scores
1 official scoreWe collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H2.23.6Primary CVE scoreVulnerability scoring details
Base CVSS 3.1 score
5.9MediumVector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H
Source materials
- CVE List V5 sourceCVE List V5
- https://kb.juniper.net/JSA11226CVE reference · x_refsource_CONFIRM
Products and packages named in the record
CWE details
CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.
Concurrent Execution using Shared Resource with Improper Synchronization ('Race Condition')
Concurrent Execution using Shared Resource with Improper Synchronization ('Race Condition') represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.
Improper Check for Unusual or Exceptional Conditions
Improper Check for Unusual or Exceptional Conditions represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.