Security readout for executives and security teams
Plain-English summary
Certain Juniper QFX and PTX network devices can be pushed into higher line-card CPU usage when handling specific traffic that is VXLAN encapsulated. This can degrade availability and become a sustained partial denial of service if the traffic continues.
Executive priority
Treat as a targeted availability risk for VXLAN-enabled Juniper data-center or backbone environments. It is not critical, but affected production devices should be patched through normal network maintenance prioritization.
Technical view
CVE-2021-31361 is improper exceptional-condition handling in Junos OS on QFX and PTX Series. An unauthenticated network attacker can send specific IP packets that are VXLAN encapsulated, increasing FPC CPU utilization and causing partial DoS. CVSS is 5.3, availability-only impact.
Likely exposure
Exposure is most relevant for Juniper QFX or PTX devices running affected Junos OS releases and processing VXLAN-encapsulated traffic. Organizations without these platforms or VXLAN use are less likely to be exposed.
Exploitation context
The bundle does not show CISA KEV listing or cited evidence of active exploitation. The vulnerability is network-reachable, unauthenticated, and low complexity, but the documented impact is limited to availability degradation.
Researcher notes
The affected-version ranges are detailed and product-specific. The sources do not provide exploit artifacts, packet details, or workarounds beyond fixed releases, so validation should focus on inventory, configuration exposure, and telemetry.
Mitigation direction
- Inventory Juniper QFX and PTX devices running Junos OS.
- Compare installed releases against Juniper JSA11223 fixed versions.
- Upgrade affected systems to a fixed Junos OS release.
- Review Juniper guidance for any interim operational mitigations.
- Prioritize devices carrying VXLAN-encapsulated production traffic.
Validation and detection
- Confirm device model, platform family, and Junos OS release.
- Verify whether VXLAN encapsulation is used on affected devices.
- Monitor FPC CPU utilization for abnormal sustained increases.
- Confirm upgraded devices run a fixed release listed by Juniper.
- Retest operational health after maintenance windows.
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-754: Exact CWE lookup
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Open ATT&CK lookupCWE-755: Exact CWE lookup
Use the exact CWE identifier as the starting point before reviewing related ATT&CK behavior. Open the exact CWE lookup page first, then review the ATT&CK searches from that MITRE weakness context. This is a Glexia lookup hint, not an official ATT&CK mapping.
Open ATT&CK lookupCVE-2021-31361 mapping review
Open the CVE-to-ATT&CK bridge for reviewed, inferred, or future official mappings tied to this CVE.
Open ATT&CK lookup- Severity
- Medium
- CVSS
- 5.3 (3.1)
- Known Exploited
- No
- Published
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
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:L/PR:N/UI:N/S:U/C:N/I:N/A:L3.91.4Primary CVE scoreVulnerability scoring details
Base CVSS 3.1 score
5.3MediumVector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
Source materials
- CVE List V5 sourceCVE List V5
- https://kb.juniper.net/JSA11223CVE 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.
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.
Improper Handling of Exceptional Conditions
Improper Handling of Exceptional Conditions represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.