Security readout for executives and security teams
Plain-English summary
CVE-2020-5135 is a critical SonicWall SonicOS firewall flaw. A remote attacker could crash affected firewalls and may be able to run arbitrary code by sending a malicious request. Because CISA lists it in KEV, treat internet-exposed SonicWall devices as urgent remediation targets.
Executive priority
Treat this as a high-priority firewall remediation issue. The vulnerable product often sits at the network edge, the CVSS score is critical, and CISA KEV confirms known exploitation. Patch governance should require rapid inventory, remediation, and executive visibility for any remaining exposed devices.
Technical view
The issue is a CWE-120 buffer overflow in SonicOS affecting listed Gen 6, SonicOSv, and Gen 7 releases. CVSS 3.1 is 9.8: network-accessible, low complexity, unauthenticated, no user interaction, with potential confidentiality, integrity, and availability impact.
Likely exposure
Exposure is most likely where affected SonicWall firewalls or SonicOSv instances run vulnerable versions and are reachable by untrusted networks. The bundle names SonicOS 6.5.4.7-79n and earlier, 6.5.1.11-4n and earlier, 6.0.5.3-93o and earlier, SonicOSv 6.5.4.4-44v-21-794 and earlier, and SonicOS 7.0.0.0-1.
Exploitation context
Active exploitation is supported by CISA KEV inclusion. The provided sources describe malicious requests causing denial of service and potentially arbitrary code execution, but do not provide exploit prevalence, affected attack surface details, or public exploit evidence beyond KEV status.
Researcher notes
Sources support remote unauthenticated attack potential, DoS, and possible arbitrary code execution, but do not include detailed root cause, exploit conditions, or fixed-release mapping in the provided bundle. Validation should focus on version evidence, exposure, and vendor advisory alignment rather than exploit reproduction.
Mitigation direction
- Identify all SonicWall SonicOS and SonicOSv assets, including virtual appliances.
- Compare versions against SonicWall PSIRT advisory SNWLID-2020-0010.
- Upgrade or remediate using SonicWall’s official guidance for affected releases.
- Prioritize internet-facing and externally reachable firewalls first.
- Restrict untrusted access to management and exposed services where operationally possible.
- Track CISA KEV remediation expectations for vulnerability management reporting.
Validation and detection
- Inventory SonicWall appliance models and SonicOS versions from management records.
- Verify each version is outside the affected ranges listed in the advisory.
- Confirm externally reachable SonicWall services are reduced to required exposure.
- Review firewall stability and security logs for unexplained crashes or suspicious request patterns.
- Document remediation status for each asset with owner and date.
- Recheck CISA KEV and SonicWall PSIRT pages for updated guidance.
Public sources used
Michael Williams reviewed this cited source version on .
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-120: 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 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-2020-5135 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
- Critical
- CVSS
- 9.8 (3.1)
- Known Exploited
- Yes
- Published
Vector: CVSS:3.1/AV:N/AC:L/PR:N/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.
CISA KEV status
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:H/I:H/A:H3.95.9Primary CVE scoreVulnerability scoring details
Base CVSS 3.1 score
9.8CriticalVector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Source materials
- CVE List V5 sourceCVE List V5
- https://psirt.global.sonicwall.com/vuln-detail/SNWLID-2020-0010CVE reference · x_refsource_CONFIRM
- https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2020-5135CVE reference · government-resource
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.
Buffer Copy without Checking Size of Input ('Classic Buffer Overflow')
Buffer Copy without Checking Size of Input ('Classic Buffer Overflow') represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.