Security readout for executives and security teams
Plain-English summary
This flaw can let an unauthenticated remote attacker crash management-related services on Juniper SRX firewalls by sending crafted HTTP traffic to J-Web. The main business risk is loss of management visibility and service disruption, not data theft or privilege gain, based on the provided sources.
Executive priority
Treat this as a high-priority availability risk for SRX firewalls, especially internet- or broadly reachable management interfaces. It does not indicate confidentiality compromise, but repeated crashes of management and supporting daemons can impair operations and incident response.
Technical view
CVE-2021-0227 is a CWE-119 buffer-boundary issue in Junos OS J-Web on SRX Series. It affects listed 17.3 through 20.1 trains before specified fixed releases. CVSS 3.1 is 7.5: network reachable, low complexity, no privileges or user interaction, with high availability impact only.
Likely exposure
Exposure is most likely where Juniper SRX Series devices run affected Junos OS versions and have J-Web reachable over HTTP management paths. Devices without exposed J-Web or already upgraded to the listed fixed releases have lower apparent exposure.
Exploitation context
The bundle does not show CISA KEV listing or cited evidence of active exploitation. The CVSS vector indicates remote, unauthenticated denial of service is plausible when J-Web processes crafted HTTP packets, but the sources do not describe public exploit availability.
Researcher notes
Evidence supports a remote unauthenticated DoS against J-Web with crashes involving web-management, ntpd, and L2CPD. The source bundle provides fixed-version thresholds but no exploit details, indicators, or confirmed exploitation. Avoid assuming compromise beyond availability impact.
Mitigation direction
- Upgrade affected SRX devices to the Juniper fixed release for their Junos OS train.
- Check Juniper advisory JSA11122 for supported workarounds or operational guidance.
- Reduce J-Web exposure according to existing management-plane access policy.
- Prioritize devices where J-Web is reachable from untrusted networks.
Validation and detection
- Inventory SRX Series devices and record Junos OS versions.
- Compare each version against the affected and fixed release matrix.
- Confirm whether J-Web is enabled and where it is reachable.
- Review logs for web-management, ntpd, or l2cpd crashes.
- After remediation, verify devices report fixed Junos OS releases.
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-119: 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-2021-0227 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
- 7.5 (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: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:L/PR:N/UI:N/S:U/C:N/I:N/A:H3.93.6Primary CVE scoreVulnerability scoring details
Base CVSS 3.1 score
7.5HighVector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Source materials
- CVE List V5 sourceCVE List V5
- https://kb.juniper.net/JSA11122CVE reference · x_refsource_MISC
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 Restriction of Operations within the Bounds of a Memory Buffer
Improper Restriction of Operations within the Bounds of a Memory Buffer represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.