Security readout for executives and security teams
Plain-English summary
This flaw lets an already authenticated Junos OS Evolved CLI user bypass command restrictions through tcpdump command handling. It does not grant a higher privilege level, but it can turn a restricted admin/operator account into broader shell access within that user's assigned privilege context.
Executive priority
Treat this as high priority for Junos OS Evolved environments using restricted administrative accounts. It can undermine operational access controls on network infrastructure, but the available sources do not indicate unauthenticated or remotely exploitable exposure.
Technical view
CVE-2021-31357 is a CWE-77 command injection issue in Junos OS Evolved tcpdump command processing/evo_tcpdump wrapper logic. With local authenticated CLI access, an attacker can bypass configured command authorization controls and execute shell commands available to the current user's privilege level. CVSS v3.1 is 7.8 High.
Likely exposure
Exposure is limited to Juniper Networks Junos OS Evolved releases before the fixed EVO versions named by Juniper. Risk is highest where restricted CLI accounts are used for operations, troubleshooting, or delegated administration.
Exploitation context
The source bundle does not show CISA KEV listing or evidence of active exploitation. Exploitation requires authenticated CLI access and no user interaction. The impact is authorization bypass and shell command execution as the current user, not privilege escalation.
Researcher notes
Affected versions include all releases before 20.3R2-S1-EVO, 20.4 before 20.4R2-S2-EVO, 21.1 before 21.1R2-EVO, and 21.2 before 21.2R1-S1-EVO/21.2R2-EVO. The flaw bypasses CLI restrictions without increasing the assigned privilege level.
Mitigation direction
- Upgrade Junos OS Evolved to the fixed version for the deployed release train.
- Prioritize devices with restricted administrator or operator CLI accounts.
- Review Juniper advisory JSA11221 for exact supported upgrade guidance.
- Restrict CLI access to trusted administrative networks and identities.
- Audit delegated accounts allowed to run tcpdump-related commands.
Validation and detection
- Inventory Junos OS Evolved devices and record exact release versions.
- Confirm no systems run versions earlier than the listed fixed EVO releases.
- Review AAA and device logs for unusual tcpdump or shell activity.
- Check login classes for restricted accounts that rely on command authorization.
- Verify remediation against Juniper advisory JSA11221.
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
Use these exact CWE pages and searches to review the Glexia ATT&CK library from this CVE's weakness and description context.
CWE-77: Command execution behavior lookup
Command injection weaknesses can lead defenders to review execution techniques and command interpreter telemetry. 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 lookupExecution behavior lookup
The CVE wording references code or command execution, so execution technique review may help defensive triage. This is a Glexia inferred lookup path, not an official MITRE, ATT&CK, or CVE Program mapping.
Open ATT&CK lookupCVE-2021-31357 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
- High
- CVSS
- 7.8 (3.1)
- Known Exploited
- No
- Published
Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/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:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H1.85.9Primary CVE scoreVulnerability scoring details
Base CVSS 3.1 score
7.8HighVector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Source materials
- CVE List V5 sourceCVE List V5
- https://kb.juniper.net/JSA11221CVE 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 Neutralization of Special Elements used in a Command ('Command Injection')
Improper Neutralization of Special Elements used in a Command ('Command Injection') represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.